Problems / RAG and retrieval, medium

OCR before every answer

A document assistant OCRs scanned pages on demand: 12 slots, 1.5 seconds per page, 15 pages a second.

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Your goals

Success ≥ 99%, p99 ≤ 10 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

15 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 OCR / document AI.Little's law: throughput ≈ concurrency ÷ latency. 200 slots at 50 ms serve about 4,000 req/s.3 replicas × 500 slots · timeout 30 s
OCR / document AIOCR / document AIAI app calls it.OCR turns scanned pages into text; layout and tables are the hard part.12 slots · 1,800 calls/min

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