System designHardsd-g275

Subject Change data captureLevel Senior–Staff~50 minCommon in Databases & SQL interviewsIndustries Technology

Question

Design a change-data-capture pipeline that keeps a search index (Elasticsearch) and a read-cache continuously in sync with a primary Postgres database for an e-commerce catalog of 50M products updated thousands of times/sec (price changes, inventory, edits). The search results can be slightly stale but must never be permanently wrong, must reflect deletes, and must survive consumer crashes and re-indexes. How do you capture changes from Postgres and propagate them reliably without dual-writes from the app?

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

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