Cache Money – junior-level system design challenge

Your database is at 95% utilization serving reads it has answered a thousand times. Cool it down below 50%.

Requirements

• Traffic: 950 req/s
• Reads : writes: 19 : 1
• p99 latency: ≤ 150 ms
• Errors: ≤ 0.5%

Goal

Hold p99 latency under 150ms, error rate under 0.5% through every stage of the test plan, then compare your design with a reference design.

The test plan

1. Steady reads: 950 requests per second.

Hint

A cache with a 90% hit ratio means only 10% of reads touch the database. Wire API → Cache → DB.

Solve it on the live simulator, free and in your browser.

Read the guide

• Design a RAG Pipeline

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