Command handlers should validate commands

Since command handlers convert commands into events, they are also responsible for validating the commands. If a command is not correctly made, or could not emit events due to the state it should not emit any events.

This is because an event holds actual change, and not the promise or failure or a change.

Reference

Hoffman, Kevin. Real-World Event Sourcing: Distribute, Evolve, and Scale Your Elixir Applications. The Pragmatic Bookshelf, 2025. The Pragmatic Programmers.

Highlights or timestamps

Real-World Event Sourcing

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