Stage 1 · Lesson 7 of 10
CDNs and edge caching
A (CDN) keeps copies of your content in data centres close to users. A visitor in Sydney gets an image from Sydney instead of Virginia. That cuts a 200 ms to 20 ms and takes load off your origin, the servers that hold the real copy.
CDNs are ideal for static files, images and video. They can cache API responses too when the headers allow it. You control them with Cache-Control headers and a (time to live), which says how long a copy counts as fresh.
Use such as app.3f9a.js, so each deploy creates a new name and never needs a purge. A fetches a file from your origin the first time someone asks for it. A push setup uploads content ahead of time.
Common trapcaching personalised responses, which can show one user another user's data.
A question to check yourself, an AI practice session and 2 cheat sheet entries come with the full roadmap. Unlock
Resources for this stage
Start with· follow one of these
- CoursePaidGrokking System Design Fundamentals
Design Gurus · Beginner · Subscription
Load balancing, API gateway, proxies, caching, CAP and Bloom filters: week 1 of the plan in order
- GitHub repoFreeThe System Design Primer
Donne Martin · Intermediate
Free: its scalability, latency, availability, CDN, load balancer and cache sections
Keep handy
Also worth your time
Why CAP only describes partitions, and what PACELC adds for normal operation