Problems / Databases, easy
A missing index makes every read take 1.5 seconds. The API gives up after 1 second and retries.
Free to open. Runs in your browser, no sign-up.
Success ≥ 99%, Apdex ≥ 0.90.
2,000 requests a second for 30 seconds: 100% 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 |
|---|---|---|
| Load balancerLoad balancer | Traffic enters here.Calls API.Layer 4 balancers route by IP and port; layer 7 balancers read HTTP and can route by path or header. | – |
| APIApp service | Load balancer forwards to it.Calls Postgres.Little's law: throughput ≈ concurrency ÷ latency. 200 slots at 50 ms serve about 4,000 req/s. | 3 replicas × 200 slots · timeout 1.0 s |
| PostgresSQL database | API calls it.Postgres runs one process per connection, which is why poolers like PgBouncer sit in front of busy databases. | 8 vCPU · 50 connections |
Try it first. Open one hint at a time if you get stuck.
Nothing is overloaded: it is just slow.
Latency is the problem; capacity follows from it.
Make the query fast (“make the database respond in 9 ms”: add the index).