Problems / Async and streaming, medium
Database changes are copied to other services by a change-data-capture connector with 8 slots, about 15 ms per change, at 1,200 changes a second.
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Success ≥ 99%, p99 ≤ 2 s.
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 4; 1 of them are hidden until then.
1,200 requests a second for 30 seconds: 100% writes.
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 Change log.Layer 4 balancers route by IP and port; layer 7 balancers read HTTP and can route by path or header. | – |
| Change logApp service | Load balancer forwards to it.Calls CDC connector (Debezium).Little's law: throughput ≈ concurrency ÷ latency. 200 slots at 50 ms serve about 4,000 req/s. | 3 replicas × 200 slots · timeout 4.0 s |
| CDC connector (Debezium)Change data capture | Change log calls it.Change data capture reads the database's write-ahead log to stream every change. | 8 slots |