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Handle Late Data in Streaming

Hard
PipelinesStream ProcessingIdempotencyData Modeling
Asked 1w ago|
Persistent Systems
Persistent Systems
Asked 58 times

Problem

You are designing a streaming pipeline where some events arrive after their event time. Those late records can invalidate previously computed windows, aggregates, or fact tables. The goal is to keep downstream data correct while limiting unnecessary recomputation.

What this tests

  • Event-time processing and watermark design
  • Idempotent writes and deduplication
  • Repair strategy for very late records
  • Data quality controls for corrected outputs

Key design signals

Common trade-off·Longer watermark vs lower latencyRecovery pattern·Targeted backfill instead of full replayPrimary challenge·Correctness under out-of-order arrival
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