Extend an Existing Endpoint Cache and Prove It with Tests
Company: Pinterest
Role: Software Engineer
Category: Software Engineering Fundamentals
Difficulty: medium
Interview Round: Onsite
Overview: Practice extending an existing endpoint cache while preserving the service's established abstraction and behavior. The answer emphasizes key isolation, hit and miss semantics, failures, invalidation, concurrent misses, and tests that prove repository call counts, tenant separation, TTL forwarding, and stale-data prevention.