Replay and backfill
On This Lesson 4 topics
This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.
In this lesson
re-process events safely, including for consumers with side effects.
Planned topics
- Replay is needed for new consumers, bug fixes, and recovery.
- Pure projections replay freely; side-effecting consumers (emails, payments) need protection.
- Techniques: idempotency keys, replay mode that disables side effects, deduplication tables.
- Throttle backfills so they do not starve live traffic.
Draft outline details
Demonstration
a consumer with a replay flag: in replay mode, update state but skip sending email; a dedupe table keyed by event id; backfill rate limit.
Check your understanding
How do you protect an email-sending consumer during replay?
Show answer
Replay mode skipping sends plus event-id deduplication.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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