Projections
Projection tracks events and project their data for specific purposes.
Communication Guide Table
Triggered by | Description |
---|---|
Event | Domain events represent business changes which have already happened |
Best Practices
{% hint style="success" %} You can/should/must...
- a projection must be idempotent
- a projection must not issue new commands or events {% endhint %}
{% hint style="warning" %} You should not...
- a projection should not query other projections. All the data of a projection must be collected from the Events' data
- a projection should not establish calls to external systems {% endhint %}