How do Redis expiration and eviction work?
Answer
Redis is an in-memory data store used for caching, coordination, queues, and fast data structures. Treat it as a capacity-bounded dependency: define expiry, invalidation, persistence, and a safe fallback when it is unavailable.
Example
Consider a production Redis change: define the expected behavior and failure modes first, implement the smallest observable change, then verify it with a focused test or measurement. The right implementation depends on the system boundary and its constraints.
Practical considerations
- Choose the approach from the requirement and constraints, not from habit.
- Include validation, error handling, and cleanup where the boundary requires them.
- Verify the observable result with focused tests or measurement.
Follow-up prompts
- What failure mode would you expect if this were implemented incorrectly?
- How would you test this behaviour?
- What changes when the feature must scale to a larger application or team?
In practice
For this medium-level topic, make assumptions explicit, choose the smallest safe implementation, and verify the behavior at the relevant boundary.