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Module
Module 5 of 6Lesson 1 of 2~16 min

CDN and caches, fast but sometimes behind

Caching makes a product fast, but it is also what sometimes shows an old version after a release. This lesson teaches you to understand the role of a CDN and of the different cache layers, to read a Cache-Control header, and to suggest ways to keep your users from seeing stale data.

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Lesson objective

By the end of this lesson, you will be able to explain the role of a CDN and of the three cache levels (browser, CDN, server), read a Cache-Control header and propose a way to keep displayed data from going stale.

Topics covered

  • CDN
  • HTTP caching
  • Cache-Control
  • web performance
  • stale data

Where it fits

Caches, CDN and environments

Why is the product fast, why does it sometimes show stale data, and why does a bug only appear in production?

Lessons in this module

  1. CDN and caches, fast but sometimes behind (this lesson)
  2. Local, preview, staging, production

What you will learn in this module

This lesson is part of the course Explain how a web product works, from browser to server

  • Explain the role of a CDN and of caches (browser, CDN, server) and anticipate their effects on speed, data freshness and releases.
  • Tell apart local, preview, staging and production environments, and say what changes from one to another (configuration, data, secrets).

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