Interview Pro Tip
Red Flag: Focusing only on what you did technically without mentioning coordination, risk mitigation, or stakeholder communication. Pro-Move: Emphasize how you de-risked (dual-write, validation, rollback) and how you aligned multiple teams.
**Situation**: We needed to migrate a petabyte-scale data lake from HDFS to S3 without disrupting 24/7 analytics used by 200+ analysts and 50+ production pipelines. **Task**: Execute migration with zero downtime and validate correctness. **Action**: I partnered with infra and data platform teams to design a multi-phase approach. (1) Dual-write for new data (HDFS + S3) so new pipelines wrote to both. (2) Background sync of historical data using DistCP with checksum validation....
The complete answer continues with detailed implementation patterns, architectural trade-offs, and production-grade considerations. It covers performance optimization strategies, common pitfalls to avoid, and real-world examples from companies like Presidio, Swiggy. The answer also includes follow-up discussion points that interviewers commonly explore.
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