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 beginner Multiple choice

    A logic bug means the last 10 days of a derived table are wrong. An engineer proposes resetting the running consumer group's offsets back 10 days and letting the job reprocess. What does that actually do?

    2 min answer offsetsconsumer-groupsreplaybackfill
  5. 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
  6. Backfill & Reprocessing advanced

    Enabling tiered storage let a platform raise log retention from 7 days to 90 days while shrinking broker disks and cutting the cluster bill roughly in half. Four months later the first 30-day reprocessing run takes 14 hours against the 3 hours the team projected from local-disk throughput. What did the saving actually buy and when does the bill arrive?

    2 min answer tiered-storageobject-storagereplayretention
  7. 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
  8. CDC to Stream intermediate

    A CDC connector on a 4 TB Postgres table is restarted with a changed configuration during business hours, and the operator does not realise this triggers a new initial snapshot. What happens over the next three hours, upstream and downstream?

    3 min answer cdcsnapshotreplication slotbackpressure
  9. 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
  10. 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
  11. CDC to Stream advanced

    A product search index is fed from a Postgres change-data-capture stream. Price and title edits appear within two seconds. For about 3% of products the indexed description is a placeholder string nobody recognises, and every affected product has a description over roughly 2 KB. Replication lag is zero and the connector reports no errors. Where is the data going?

    3 min answer postgresdebeziumtoastreplica-identity
  12. 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