Explain Event Sourcing architecture in enterprise PHP systems.

Event Sourcing stores immutable domain events instead of current state, enabling auditability, replayability, temporal queries, and highly scalable architectures.

Event Sourcing is an architectural pattern where every state change is stored as an immutable event rather than updating mutable database rows.

Traditional CRUD systems store only current state. Example:

Event Sourcing stores every transition:

The current state becomes a projection derived from replaying events.

Core concepts:

Events represent facts that already happened. They must never change retroactively.

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