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Event Replay - Junior

A projection is a query-friendly view derived from events. New logic, corruption, or a new index may require rebuilding it.

flowchart LR Events --> V1[Old projection logic] Events --> V2[New projection logic]
Updating the live table in place risks mixed old/new semantics and downtime. An immutable retained log allows deterministic reconstruction if handlers remain compatible and idempotent.

Test yourself

  1. What is a projection?
  2. Why rebuild from events?
  3. Why not overwrite the live view immediately? Continue to middle.md.