Problems / RAG and retrieval, hard

Corrective RAG evaluator bottleneck

Corrective RAG grades retrieved chunks with an evaluator model before answering. The evaluator has 20 slots and grades every question.

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

Your goals

Success ≥ 99%, p99 ≤ 5 s.

The traffic

60 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 Hybrid search, Retrieval evaluator, 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
Hybrid searchHybrid searchAI app calls it.Hybrid search combines keyword matching (BM25) with vector similarity.400 slots · 2 steps
Retrieval evaluatorLLM-as-judgeAI app calls it.An LLM judge grades outputs at scale, but it is another model call with its own latency, cost and biases.20 slots
GPU serving poolSelf-hosted serving poolAI app calls it.GPU servers batch requests together; throughput rises with batch size until memory runs out.400 slots

Hints

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

Hint 1

The evaluator is a model call per question.

Hint 2

Follow one question through each retrieval stage; the stage that turns red is the one to fix first.

One way to solve it

Give the evaluator more capacity.

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