Problems / LLM serving, medium

PII redaction on the hot path

Every prompt is scanned by a PII redactor with 2 vCPUs and 10 ms of CPU per prompt, at 400 requests a second.

Free to open. Runs in your browser, no sign-up.

Your goals

Success ≥ 99%, p99 ≤ 5 s.

The traffic

400 requests a second for 30 seconds: 100% request (reads).

The system

What each component does in this design, and what calls it. The simulator mimics each one from these settings.

ComponentIts job hereSettings
Load balancerLoad balancerTraffic enters here.Calls AI app.Layer 4 balancers route by IP and port; layer 7 balancers read HTTP and can route by path or header.–
AI appApp serviceLoad balancer forwards to it.Calls PII redactor, GPU serving pool.Little's law: throughput ≈ concurrency ÷ latency. 200 slots at 50 ms serve about 4,000 req/s.3 replicas × 500 slots · timeout 30 s
PII redactorPII redactorAI app calls it.Redacting personal data before it reaches a model or a log reduces privacy and compliance risk.400 slots
GPU serving poolSelf-hosted serving poolAI app calls it.GPU servers batch requests together; throughput rises with batch size until memory runs out.2000 slots

Hints

Try it first. Open one hint at a time if you get stuck.

Hint 1

CPU needed = 400 × 10 ms = 4 vCPUs.

Hint 2

Redaction runs before every call.

One way to solve it

Give the redactor more capacity and CPU.

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