An independent, general engineering perspective; not a description of proprietary systems or employer-specific work.
Assume you will replay
Every evolving data system eventually encounters incorrect logic, missed records, or late-arriving events. Make the correction path part of normal operations.
Favor idempotent work
Retries and historical reprocessing should converge on correct state. Define stable record identity and safe write semantics before automation.
Control the blast radius
Bound concurrency, isolate workloads, add dry-run modes, and expose checkpoints. Operators should be able to resume without starting from scratch.
Verify the output
Compare counts, checksums, and domain-specific invariants. An apparently successful job is not necessarily a correct result.