Problems / Cloud and cost, medium
A web fleet runs on 2 EC2 instances in an Auto Scaling group that tracks 50% CPU. At 2 minutes a TV ad triples traffic for 10 minutes. Target tracking needs 3 one-minute periods above target, then each new instance takes about 3 minutes to boot and pass health checks.
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Keep success at 99% or more through the ad.
Like a coding problem, a solution has to pass every case, not just the one it was built for. Submit in the lab runs all 3; 1 of them are hidden until then.
75 requests a second for 900 seconds: 100% web (reads).
What each component does in this design, and what calls it. The simulator mimics each one from these settings.
| Component | Its job here | Settings |
|---|---|---|
| Application Load BalancerLoad balancer | Traffic enters here.Calls Web fleet (EC2 Auto Scaling).Layer 4 balancers route by IP and port; layer 7 balancers read HTTP and can route by path or header. | – |
| Web fleet (EC2 Auto Scaling)Autoscaling group | Application Load Balancer forwards to it.Calls Aurora Postgres.Autoscalers add instances when a metric stays high, but new instances take minutes to be ready. | 200 slots · 2–12 instances |
| Aurora PostgresSQL database | Web fleet (EC2 Auto Scaling) calls it.Postgres runs one process per connection, which is why poolers like PgBouncer sit in front of busy databases. | 16 vCPU · 300 connections |