The 60-second answer
Define query types, visibility/privacy, freshness SLA, expiration/deletion semantics, and ranking objective before choosing retrieval technology. Maintain a rapidly updated lexical/vector index with strict ACL filtering and expiration propagation; combine semantic relevance with recency and social/context signals.
Build the answer in this order
Define query types, visibility/privacy, freshness SLA, expiration/deletion semantics, and ranking objective before choosing retrieval technology.
Maintain a rapidly updated lexical/vector index with strict ACL filtering and expiration propagation; combine semantic relevance with recency and social/context signals.
Use candidate retrieval followed by ranking, with caches that respect visibility and deletion invalidation.
Evaluate recall/relevance, freshness lag, deletion correctness, latency, and abuse/safety slices.
A useful interview mental model
This is the shape of a strong answer—not a script to memorize.
Senior-level signal
- Senior answers treat privacy and deletion as correctness requirements, not post-ranking filters.
- Discuss index backfill, hot-key/fanout behavior, and how to avoid stale cached results after privacy changes.
What the interviewer is really testing
Likely follow-up questions
Common weak-answer patterns
- Jumping to a model before defining the product contract.
- Listing components without bottlenecks, metrics, or failure handling.
- Ignoring data quality, serving latency, monitoring, and iteration.