System designHardsd-g193

Subject Data lineageLevel Senior–Staff~45 minCommon in Distributed systems interviewsIndustries Technology, Software development

Question

Under GDPR/CCPA, when a user requests deletion you must erase their personal data everywhere it propagated — but their PII has flowed from the source app DB through dozens of ETL jobs into warehouse tables, ML feature stores, derived aggregates, search indexes, caches, and analytics exports. Design a system that tracks where each user's PII lands and can fulfill a 'delete me' request completely and provably within the legal window, without breaking downstream tables that legitimately need aggregates. ~100M users, hundreds of datasets.

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.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.