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The URL Shortening App
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</label>
<div class="md-search" data-md-component="search" role="dialog">
<label class="md-search__overlay" for="__search"></label>
<div class="md-search__inner" role="search">
<form class="md-search__form" name="search">
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</button>
</nav>
</form>
<div class="md-search__output">
<div class="md-search__scrollwrap" data-md-scrollfix>
<div class="md-search-result" data-md-component="search-result">
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</div>
</div>
</div>
</div>
</nav>
</header>
<div class="md-container" data-md-component="container">
<main class="md-main" data-md-component="main">
<div class="md-main__inner md-grid">
<div class="md-sidebar md-sidebar--primary" data-md-component="sidebar" data-md-type="navigation" >
<div class="md-sidebar__scrollwrap">
<div class="md-sidebar__inner">
<!-- Determine classes -->
<!-- Navigation -->
<nav
class="md-nav md-nav--primary"
aria-label="Navigation"
data-md-level="0"
>
<!-- Repository information -->
<!-- Navigation list -->
<ul class="md-nav__list" data-md-scrollfix>
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../.." class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Home
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--active md-nav__item--section md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2"
checked
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2"
id="__nav_2_label"
tabindex=""
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Level 101
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<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="1"
aria-labelledby="__nav_2_label"
aria-expanded="true"
>
<label class="md-nav__title" for="__nav_2">
<span class="md-nav__icon md-icon"></span>
Level 101
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_1"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_1"
id="__nav_2_1_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Fundamentals Series
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<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_1_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_1">
<span class="md-nav__icon md-icon"></span>
Fundamentals Series
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_1_1"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_1_1"
id="__nav_2_1_1_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Linux Basics
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_1_1_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_1_1">
<span class="md-nav__icon md-icon"></span>
Linux Basics
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_basics/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_basics/command_line_basics/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Command Line Basics
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_basics/linux_server_administration/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Server Administration
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_basics/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_1_2"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_1_2"
id="__nav_2_1_2_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Git
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_1_2_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_1_2">
<span class="md-nav__icon md-icon"></span>
Git
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../git/git-basics/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Git Basics
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../git/branches/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Working With Branches
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../git/github-hooks/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Github and Hooks
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../git/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_1_3"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_1_3"
id="__nav_2_1_3_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Linux Networking
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_1_3_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_1_3">
<span class="md-nav__icon md-icon"></span>
Linux Networking
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_networking/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_networking/dns/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
DNS
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_networking/udp/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
UDP
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_networking/http/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
HTTP
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_networking/tcp/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
TCP
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_networking/ipr/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Routing
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_networking/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--active md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_2"
checked
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_2"
id="__nav_2_2_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Python and Web
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_2_label"
aria-expanded="true"
>
<label class="md-nav__title" for="__nav_2_2">
<span class="md-nav__icon md-icon"></span>
Python and Web
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../python-concepts/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Some Python Concepts
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../python-web-flask/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Python, Web and Flask
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item md-nav__item--active">
<!-- State toggle -->
<input
class="md-nav__toggle md-toggle"
type="checkbox"
id="__toc"
/>
<!-- Hack: see partials/toc.html for more information -->
<!-- Navigation link to table of contents -->
<label class="md-nav__link md-nav__link--active" for="__toc">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
The URL Shortening App
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<a
href="./"
class="md-nav__link md-nav__link--active"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
The URL Shortening App
</span>
<!-- Navigation link status -->
</a>
<!-- Table of contents -->
<nav class="md-nav md-nav--secondary" aria-label="Table of contents">
<label class="md-nav__title" for="__toc">
<span class="md-nav__icon md-icon"></span>
Table of contents
</label>
<ul class="md-nav__list" data-md-component="toc" data-md-scrollfix>
<li class="md-nav__item">
<a href="#design" class="md-nav__link">
<span class="md-ellipsis">
Design
</span>
</a>
<nav class="md-nav" aria-label="Design">
<ul class="md-nav__list">
<li class="md-nav__item">
<a href="#1-high-level-operations-and-api-endpoints" class="md-nav__link">
<span class="md-ellipsis">
1. High Level Operations and API Endpoints
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#2-how-to-shorten" class="md-nav__link">
<span class="md-ellipsis">
2. How to shorten?
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#3-is-url-valid" class="md-nav__link">
<span class="md-ellipsis">
3. Is URL Valid?
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#4-storage" class="md-nav__link">
<span class="md-ellipsis">
4. Storage
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#5-other" class="md-nav__link">
<span class="md-ellipsis">
5. Other
</span>
</a>
</li>
</ul>
</nav>
</li>
</ul>
</nav>
</li>
<!-- Navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../sre-conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_3"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_3"
id="__nav_2_3_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Data
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_3_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_3">
<span class="md-nav__icon md-icon"></span>
Data
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_3_1"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_3_1"
id="__nav_2_3_1_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Relational Databases
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_3_1_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_3_1">
<span class="md-nav__icon md-icon"></span>
Relational Databases
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
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<!-- Navigation link status -->
</a>
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<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/concepts/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Key Concepts
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<!-- Navigation link status -->
</a>
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<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/mysql/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
MySQL
</span>
<!-- Navigation link status -->
</a>
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<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/innodb/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
InnoDB
</span>
<!-- Navigation link status -->
</a>
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/backup_recovery/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Backup and Recovery
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<!-- Navigation link status -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/replication/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
MySQL Replication
</span>
<!-- Navigation link status -->
</a>
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/operations/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Operational Concepts
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/select_query/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Select Query
</span>
<!-- Navigation link status -->
</a>
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<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/query_performance/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Query Performance
</span>
<!-- Navigation link status -->
</a>
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<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/lab/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Lab
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_sql/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_3_2"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_3_2"
id="__nav_2_3_2_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
NoSQL
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_3_2_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_3_2">
<span class="md-nav__icon md-icon"></span>
NoSQL
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_nosql/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_nosql/key_concepts/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Key Concepts
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../databases_nosql/further_reading/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_3_3"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_3_3"
id="__nav_2_3_3_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Message Queue
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_3_3_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_3_3">
<span class="md-nav__icon md-icon"></span>
Message Queue
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../messagequeue/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../messagequeue/key_concepts/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Key Concepts
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../messagequeue/further_reading/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_3_4"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_3_4"
id="__nav_2_3_4_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Big Data
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_3_4_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_3_4">
<span class="md-nav__icon md-icon"></span>
Big Data
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../big_data/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../big_data/evolution/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Evolution and Architecture of Hadoop
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../big_data/tasks/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_4"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_4"
id="__nav_2_4_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Systems Design
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_4_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_4">
<span class="md-nav__icon md-icon"></span>
Systems Design
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../systems_design/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../systems_design/scalability/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Scalability
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../systems_design/availability/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Availability
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../systems_design/fault-tolerance/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Fault Tolerance
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../systems_design/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_5"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_5"
id="__nav_2_5_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Metrics and Monitoring
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_5_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_5">
<span class="md-nav__icon md-icon"></span>
Metrics and Monitoring
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../metrics_and_monitoring/introduction/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../metrics_and_monitoring/command-line_tools/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Command-line Tools
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../metrics_and_monitoring/third-party_monitoring/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Third-party Monitoring
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../metrics_and_monitoring/alerts/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Proactive Monitoring with Alerts
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../metrics_and_monitoring/best_practices/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Best Practices for Monitoring
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../metrics_and_monitoring/observability/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Observability
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../metrics_and_monitoring/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_6"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_6"
id="__nav_2_6_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Security
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_6_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_6">
<span class="md-nav__icon md-icon"></span>
Security
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../security/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../security/fundamentals/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Fundamentals of Security
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../security/network_security/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Network Security
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../security/threats_attacks_defences/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Threat, Attacks & Defences
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../security/writing_secure_code/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Writing Secure code
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../security/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--section md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3"
id="__nav_3_label"
tabindex=""
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Level 102
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="1"
aria-labelledby="__nav_3_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3">
<span class="md-nav__icon md-icon"></span>
Level 102
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_1"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_1"
id="__nav_3_1_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Linux Intermediate
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_1_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_1">
<span class="md-nav__icon md-icon"></span>
Linux Intermediate
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/linux_intermediate/introduction/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/linux_intermediate/package_management/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Package Management
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/linux_intermediate/storage_media/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Storage Media
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/linux_intermediate/archiving_backup/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Archiving and Backup
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/linux_intermediate/introvim/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction to Vim
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/linux_intermediate/bashscripting/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Bash Scripting
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/linux_intermediate/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_2"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_2"
id="__nav_3_2_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Linux Advanced
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_2_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_2">
<span class="md-nav__icon md-icon"></span>
Linux Advanced
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_2_1"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_2_1"
id="__nav_3_2_1_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Containerization And Orchestration
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_3_2_1_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_2_1">
<span class="md-nav__icon md-icon"></span>
Containerization And Orchestration
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/containerization_and_orchestration/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/containerization_and_orchestration/intro_to_containers/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction To Containers
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/containerization_and_orchestration/containerization_with_docker/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Containerization With Docker
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/containerization_and_orchestration/orchestration_with_kubernetes/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Orchestration With Kubernetes
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/containerization_and_orchestration/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_2_2"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_2_2"
id="__nav_3_2_2_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
System Calls and Signals
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_3_2_2_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_2_2">
<span class="md-nav__icon md-icon"></span>
System Calls and Signals
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_calls_and_signals/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_calls_and_signals/signals/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Signals
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_calls_and_signals/system_calls/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
System Calls
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_calls_and_signals/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_3"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_3"
id="__nav_3_3_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Networking
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_3_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_3">
<span class="md-nav__icon md-icon"></span>
Networking
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/networking/introduction/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/networking/security/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Security
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/networking/scale/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Scale
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/networking/rtt/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
RTT
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/networking/infrastructure-features/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Infrastructure Services
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/networking/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_4"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_4"
id="__nav_3_4_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
System Design
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_4_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_4">
<span class="md-nav__icon md-icon"></span>
System Design
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_design/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_design/large-system-design/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Large System Design
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_design/scaling/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Scaling
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_design/scaling-beyond-the-datacenter/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Scaling Beyond the Data Center
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_design/resiliency/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Resiliency
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_design/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_5"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_5"
id="__nav_3_5_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
System Troubleshooting and Performance Improvements
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_5_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_5">
<span class="md-nav__icon md-icon"></span>
System Troubleshooting and Performance Improvements
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_troubleshooting_and_performance/introduction/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_troubleshooting_and_performance/troubleshooting/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Troubleshooting
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_troubleshooting_and_performance/important-tools/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Important Tools
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_troubleshooting_and_performance/performance-improvements/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Performance Improvements
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_troubleshooting_and_performance/troubleshooting-example/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Troubleshooting Example
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/system_troubleshooting_and_performance/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_6"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_6"
id="__nav_3_6_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Continuous Integration and Continuous Delivery
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_6_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_6">
<span class="md-nav__icon md-icon"></span>
Continuous Integration and Continuous Delivery
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/continuous_integration_and_continuous_delivery/introduction/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level102/continuous_integration_and_continuous_delivery/introduction_to_cicd/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
What is CI/CD?
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
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<h1 id="the-url-shortening-app">The URL Shortening App</h1>
<p>Let's build a very simple URL-shortening app using Flask and try to incorporate all aspects of the development process including the reliability aspects. We will not be building the UI and we will come up with a minimal set of API that will be enough for the app to function well.</p>
<h2 id="design">Design</h2>
<p>We don't jump directly to coding. First thing we do is gather requirements. Come up with an approach. Have the approach/design reviewed by peers. Evolve, iterate, document the decisions and tradeoffs. And then finally implement. While we will not do the full blown design document here, we will raise certain questions here that are important to the design.</p>
<h3 id="1-high-level-operations-and-api-endpoints">1. High Level Operations and API Endpoints</h3>
<p>Since it's a URL-shortening app, we will need an API for generating the shorten link given an original link. And an API/Endpoint which will accept the shorten link and redirect to original URL. We are not including the user aspect of the app to keep things minimal. These two API should make app functional and usable by anyone.</p>
<h3 id="2-how-to-shorten">2. How to shorten?</h3>
<p>Given a URL, we will need to generate a shortened version of it. One approach could be using random characters for each link. Another thing that can be done is to use some sort of hashing algorithm. The benefit here is we will reuse the same hash for the same link. Ie: if lot of people are shortening <code>https://www.linkedin.com</code>, they all will have the same value, compared to multiple entries in DB if chosen random characters.</p>
<p>What about hash collisions? Even in random characters approach, though there is a less probability, hash collisions can happen. And we need to be mindful of them. In that case, we might want to prepend/append the string with some random value to avoid conflict.</p>
<p>Also, choice of hash algorithm matters. We will need to analyze algorithms. Their CPU requirements and their characteristics. Choose one that suits the most.</p>
<h3 id="3-is-url-valid">3. Is URL Valid?</h3>
<p>Given a URL to shorten, how do we verify if the URL is valid? Do we even verify or validate? One basic check that can be done is see if the URL matches a regex of a URL. To go even further, we can try opening/visiting the URL. But there are certain gotchas here.</p>
<ol>
<li>We need to define success criteria. ie: HTTP 200 means it is valid.</li>
<li>What if the URL is in private network?</li>
<li>What if URL is temporarily down?</li>
</ol>
<h3 id="4-storage">4. Storage</h3>
<p>Finally, storage. Where will we store the data that we will generate over time? There are multiple database solutions available and we will need to choose the one that suits this app the most. Relational database like MySQL would be a fair choice but <strong>be sure to checkout School of SRE's <a href="../../databases_sql/intro/">SQL database section</a> and <a href="../../databases_nosql/intro/">NoSQL databases section</a> for deeper insights into making a more informed decision.</strong></p>
<h3 id="5-other">5. Other</h3>
<p>We are not accounting for users into our app and other possible features like rate limiting, customized links, etc. but it will eventually come up with time. Depending on the requirements, they too might need to get incorporated.</p>
<p>The minimal working code is given below for reference, but I'd encourage you to come up with your own.</p>
<pre><code class="language-python">from flask import Flask, redirect, request
from hashlib import md5
app = Flask(&quot;url_shortener&quot;)
mapping = {}
@app.route(&quot;/shorten&quot;, methods=[&quot;POST&quot;])
def shorten():
global mapping
payload = request.json
if &quot;url&quot; not in payload:
return &quot;Missing URL Parameter&quot;, 400
# TODO: check if URL is valid
hash_ = md5()
hash_.update(payload[&quot;url&quot;].encode())
digest = hash_.hexdigest()[:5] # limiting to 5 chars. Less the limit more the chances of collission
if digest not in mapping:
mapping[digest] = payload[&quot;url&quot;]
return f&quot;Shortened: r/{digest}\n&quot;
else:
# TODO: check for hash collission
return f&quot;Already exists: r/{digest}\n&quot;
@app.route(&quot;/r/&lt;hash_&gt;&quot;)
def redirect_(hash_):
if hash_ not in mapping:
return &quot;URL Not Found&quot;, 404
return redirect(mapping[hash_])
if __name__ == &quot;__main__&quot;:
app.run(debug=True)
&quot;&quot;&quot;
OUTPUT:
===&gt; SHORTENING
$ curl localhost:5000/shorten -H &quot;content-type: application/json&quot; --data '{&quot;url&quot;:&quot;https://linkedin.com&quot;}'
Shortened: r/a62a4
===&gt; REDIRECTING, notice the response code 302 and the location header
$ curl localhost:5000/r/a62a4 -v
* Uses proxy env variable NO_PROXY == '127.0.0.1'
* Trying ::1...
* TCP_NODELAY set
* Connection failed
* connect to ::1 port 5000 failed: Connection refused
* Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 5000 (#0)
&gt; GET /r/a62a4 HTTP/1.1
&gt; Host: localhost:5000
&gt; User-Agent: curl/7.64.1
&gt; Accept: */*
&gt;
* HTTP 1.0, assume close after body
&lt; HTTP/1.0 302 FOUND
&lt; Content-Type: text/html; charset=utf-8
&lt; Content-Length: 247
&lt; Location: https://linkedin.com
&lt; Server: Werkzeug/0.15.4 Python/3.7.7
&lt; Date: Tue, 27 Oct 2020 09:37:12 GMT
&lt;
&lt;!DOCTYPE HTML PUBLIC &quot;-//W3C//DTD HTML 3.2 Final//EN&quot;&gt;
&lt;title&gt;Redirecting...&lt;/title&gt;
&lt;h1&gt;Redirecting...&lt;/h1&gt;
* Closing connection 0
&lt;p&gt;You should be redirected automatically to target URL: &lt;a href=&quot;https://linkedin.com&quot;&gt;https://linkedin.com&lt;/a&gt;. If not click the link.
&quot;&quot;&quot;
</code></pre>
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