Idempotency, checkpointing and self-healing recovery aren't luxuries — they're the price of sleeping through the night.
End-to-end exactly-once is really at-least-once plus idempotency. Getting that right changes how you design every sink.
Late data is normal, not an edge case. Watermarks and windowing handle stragglers without reprocessing the world.
The dual-write, reconcile, and cutover strategy that moved a legacy warehouse to Delta without anyone noticing.
not_null and unique are table stakes. These are the semantic tests that have saved me from silent data incidents.
Safe backfills need idempotency, partitioning, and a throttle. The pattern that lets me reprocess a year of data with confidence.
Monitoring business metrics is too late. Catch breakage at the schema boundary with contracts — before it flows downstream.