Free HLD round · 12 minutes

Design a cached redirect service

Round time 12:00

Requirements

At 1,000 redirect requests per second, several service instances read the same short-code mappings. Each mapping contains a destination URL and an optional expires_at timestamp.

Return a redirect for a live code and an expired response after its deadline.
Use a cache for repeated reads and a durable mapping store for recovery.
Show the cache-hit path and what happens on a cache miss or restart.
Explain expiry checks in labels or notes. Cache eviction must not delete the durable mapping.

Link creation, analytics and multi-region replication are outside this sample.

Core requirements

0/3

Trace a cache hit and a cache miss from the browser to the redirect service.
Explain how an expired link stops resolving even when a cached copy exists.
Explain how readers recover mappings after the cache or process restarts.

Draw the read path

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Design a cached redirect service

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