In MIPC, what does event sourcing store to enable replay?

• A. A sequence of domain events; allows reconstructing state by replay.
• B. The code of the application.
• C. A single snapshot only.
• D. Only messages to the queue.

Answer: (B)

Event sourcing achieves replay by storing an ordered history of domain events, each representing a state change. Instead of keeping only the current state, the system records every change in the exact sequence it occurred. To reconstruct the current state, you start from the initial state and replay each event in order, applying the changes described by those events. This history is the source of truth, and it also supports auditing and debugging because you can see precisely how the state evolved over time. For performance, you can take periodic snapshots of the state and replay only the events that happened after the latest snapshot. The key idea is that replay relies on the sequence of events that captured what happened, not on the application code or message queues.