Data Migration Strategies: Zero-Downtime Patterns, CDC, Dual Writes, and Proving Correctness
A practical guide to production data migration strategies—big-bang vs online migrations, expand/contract, dual writes, CDC, validation, cutover, and rollback. Includes runnable code, mermaid diagrams, and trade-offs commonly tested in system design interviews.
ETL vs ELT: Production Tradeoffs, Modern Lakehouse Patterns, and Interview-Ready Reasoning
A production-focused guide to ETL vs ELT that explains where transformations run, how that impacts cost, governance, and latency, and how to justify the right choice in system design interviews.