Problems / Cloud and cost, easy
Traffic climbs steadily to 6× over 15 minutes. The Auto Scaling group tracks 50% CPU, which is plenty of time to react, but its maximum size is 3 instances.
Unlock it once for 10 credits; everything inside it is free (runs, changes, Submit, results, hints). Sign in with Google to start; new accounts get free credits.
Keep success at 99% or more as traffic climbs.
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.
60 requests a second, ramping to 6× 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 · 2–3 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 |