1. Backfill & Reprocessing advanced

    A bug in a streaming job produced wrong results for three weeks. How should the backfill be designed so it does not cause a second incident?

    3 min answer backfillreprocessingreplayversioning
  2. Backfill & Reprocessing advanced

    A bug is found in a stream processor that has been running for a month. How should the correction be handled?

    2 min answer confluentreprocessingreplayidempotency
  3. Backfill & Reprocessing advanced

    A logic bug means six months of a derived table are wrong. You must reprocess without disrupting live consumers. How?

    2 min answer data-platformbackfillreprocessingcorrectness
  4. Backfill & Reprocessing advanced

    A transformation bug means months of derived data are wrong. What makes reprocessing feasible, and what breaks it?

    2 min answer backfillreprocessingretentionisolation
  5. Backfill & Reprocessing advanced

    You reprocess six months of events through an updated job to fix a calculation error. Support is flooded with customer complaints. What went wrong?

    2 min answer replayside-effectsdesign
  6. CDC to Stream advanced

    A catalogue search index is rebuilt every night by a full extract of a 60-million-row product table. You must move it onto a change-data-capture stream with no search downtime and no window where the index is silently wrong. Sequence it so each step is reversible, and say where the point of no return is.

    3 min answer cdcsearch-indexingdivergencereversibility
  7. CDC to Stream advanced

    A platform publishes database changes as a stream for many consumers. What must the published stream provide that the raw change log does not?

    2 min answer cdccontractscouplingtransformation
  8. CDC to Stream advanced

    A service rebuilds its cache from a compacted topic after being offline for two weeks. It now holds records that were deleted. Why?

    2 min answer compactiontombstonescorrectness
  9. CDC to Stream advanced

    A team proposes exposing their service's database change stream via CDC so other teams can consume it, avoiding the work of building an event API. What is your assessment?

    2 min answer cdcintegrationcouplingcontracts
  10. Exactly-Once Semantics advanced

    A payments team requires exactly-once processing of a transaction stream. What is actually achievable, and what should be built?

    2 min answer phonepeexactly-onceidempotencytransactions
  11. Exactly-Once Semantics advanced

    A team requires exactly-once processing across a message platform and its external providers. What is achievable, and what should be built instead?

    2 min answer exactly-onceidempotencyat-least-onceboundaries
  12. Exactly-Once Semantics advanced

    A team wants exactly-once processing in a streaming pipeline. Where do transactional producers, idempotent consumers and output-side deduplication each fit, and which failure modes still require reconciliation?

    3 min answer kafkaexactly-onceidempotencytransactions