cloudpatterns.appClassroomKatasWhiteboardBlog
Scale LineLesson

A CDN for the files everyone wants

Put copies of popular files on edge servers near users — the origin sees only the misses, the views arrive sooner, and the cache rules decide what may be shared and for how long.

12 minMediumStation: CDN (content delivery network)

Members lesson

Membership isn’t open yet. The free lessons are open — 16 of them, including the whole first leg of the Scale Line.

Start a free lessonSee the map
  1. Users
  2. Storage
From step 1 — Every view travels to the bucket and back — 900 requests a second, for the same photo each time.

What you'll be able to do

  1. 1Predict the load on the origin for a given CDN hit ratio.
  2. 2Explain why answering from an edge near the user cuts latency.
  3. 3Choose what goes behind a CDN and how long it may be cached (TTL, versioned file names).

Inside the lesson

steps
9
questions
10
simulations
2

You guess first, then run the system and see if you were right.

Step 1 · The setup

A celebrity shares a Pixel photo: 900 views a second, from people all over the map. Pixel's photo viewer fetches every one of them from the bucket.

Watch the bucket's request count.

Steps 2–9 are for members

More on the Scale Line

  1. Latency & percentilesOpen8 min
  2. Server capacity & scaling upFree with an account10 min
  3. Split app and database tiersFree with an account10 min
  4. Load balancerFree with an account10 min
  5. Horizontal scaling with a stateless tierFree with an account10 min
  6. Cache-asideFree with an account10 min
  7. Object storage for user filesMembers10 min
  8. Read replicas for a read-heavy appMembers11 min