Caching Strategies and In Memory Storage Questions
Understanding caching mechanisms (HTTP caching, application-level caching with Redis/Memcached). Cache invalidation strategies, TTL, and when to cache. Performance implications.
EasyTechnical
0 practiced
Explain what a cache stampede (thundering herd) is, why it can overwhelm origin services, and list common mitigations such as mutex locks for recomputation, request coalescing (singleflight), randomized TTLs, early recompute, and pre-warming. Provide a short example of when randomized TTLs reduce stampedes.
EasyTechnical
0 practiced
Explain HTTP caching headers and semantics in detail: describe Cache-Control directives (max-age, no-cache, no-store, must-revalidate), ETag and conditional GETs, Last-Modified and Expires. For each header explain how browsers and intermediary caches behave, and give a concrete scenario where ETag-based validation is preferred over purely time-based max-age.
MediumTechnical
0 practiced
List security considerations when using in-memory caches (Redis, Memcached) in production: network exposure, authentication, TLS for in-transit encryption, role-based access, ACLs, protecting sensitive PII, injection and poisoning risks, and compliance obligations. Provide practical mitigations for each concern.
MediumTechnical
0 practiced
You observe p99 latency for Redis rising intermittently from 1ms to 50ms. Provide a step-by-step troubleshooting checklist: which Redis stats/commands to run (INFO, SLOWLOG, LATENCY), OS-level metrics (CPU, mem, IO), configuration flags to inspect, and likely causes such as large keys, persistence (RDB/AOF), background saves, fragmentation, or slow commands.
HardSystem Design
0 practiced
Design a system to serve analytics dashboards with sub-second latency by caching pre-aggregated time-series keys. Describe cache key schema for aggregates, freshness/retention windows, incremental update strategies for streaming data, how to handle ad-hoc queries, and trade-offs between precomputation memory and query flexibility.
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