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Scale LineLesson

Autoscaling that keeps up

Let the fleet grow and shrink with traffic — but new instances arrive late, so keep a minimum with headroom, leave a margin between the thresholds, and autoscale only stateless tiers.

12 minMediumStation: Autoscaling

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. Web API
From step 1 — Traffic swings from 550 requests a second at the peak to 50 at night.

What you'll be able to do

  1. 1Predict the instance count over a traffic curve, given the thresholds and the time a new instance takes to start.
  2. 2Explain why autoscaling reacts late to a sudden spike, and how a minimum and headroom cover the gap.
  3. 3Choose the scaling metric and thresholds — CPU, response time or queue length — and which tiers can autoscale at all.

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

Pixel's traffic climbs every evening and falls away at night. Its web tier is sized for the evening peak — four large instances, all day long.

Watch a day go by — squeezed into two minutes — and follow the CPU bar.

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. A CDN for the files everyone wantsMembers12 min