Problems / Databases, medium

Object storage: one hot prefix

All images live under one key prefix, which the store limits to about 5,500 reads a second. Reads arrive at 7,000 a second.

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Your goals

Success ≥ 99%.

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 5; 1 of them are hidden until then.

  1. As given. The problem’s own traffic, scheduled failures and seed.
  2. Peak hour. 25% more traffic than the problem states, with the same failures.
  3. A slow dependency. The main data store or model answers twice as slowly for part of the run.
  4. A server dies. One replica of the service with the most replicas is killed for part of the run.

The traffic

7,000 requests a second for 30 seconds: 100% 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 Media API.Layer 4 balancers route by IP and port; layer 7 balancers read HTTP and can route by path or header.–
Media APIApp serviceLoad balancer forwards to it.Calls Object storage (one prefix).Little's law: throughput ≈ concurrency ÷ latency. 200 slots at 50 ms serve about 4,000 req/s.4 replicas × 200 slots · timeout 4.0 s
Object storage (one prefix)Object storageMedia API calls it.Object stores like S3 keep copies across devices and facilities for very high durability.5000 slots · 330,000 calls/min

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