What is a projection?

A projection turns a stream of events into state.

Decissions taken by the system are recorded as events on an event stream.

However, humans may have a hard time understanding the state of the system by looking at this stream of events.

It is the responsibility of a projection to summarize the decissions taken in the past, into a human readable format of the state at a given point in time.

When to use it?

Use this pattern every time a user needs to see the current state of the system.

Want to give it a try?

Check out the quickstart for a quick example.

Or get started with the learning path, where you'll build a Projection yourself in lesson 4.