Problems / RAG and retrieval, medium

Re-indexing 100 million documents

An ingestion service parses, chunks and embeds documents for search. A re-index of 100 million documents pushes 80 documents a second through it, but it has 20 slots at about half a second per document.

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Your goals

Success ≥ 99%, p99 ≤ 5 s.

Test cases

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.

  1. As given. The problem’s own traffic, scheduled failures and seed.
  2. A server dies. One replica of the service with the most replicas is killed for part of the run.

The traffic

80 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 Ingestion workers.Little's law: throughput ≈ concurrency ÷ latency. 200 slots at 50 ms serve about 4,000 req/s.3 replicas × 500 slots · timeout 30 s
Ingestion workersDocument ingestionAI app calls it.Ingestion splits documents into chunks before they are embedded for retrieval.20 slots

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