Learning Akka (Video 18)

This video tutorial explores the CQRS pattern, highlighting its separation of read and write operations compared to the CRUD system. It delves into persistence queries, explaining their role in reading persistent events from a Journal and migrating data between write and query sides. The tutorial covers predefined query types and demonstrates implementing a view for a persistent actor using persistence queries. The session concludes with a summary and a look ahead to Akka cluster.

What is the main distinction between CQRS and the traditional CRUD system?

• CQRS combines read and write operations.

• CQRS separates read and write operations.

• CRUD uses two models for operations.

• CRUD separates read and write operations.

What is the primary use of persistence queries in CQRS?

• To update events in the Journal.

• To migrate data from the write side to the query side.

• To delete events from the Journal.

• To write data to the Journal.

Which query type allows you to read events from a specific persistent actor?

• Events by tag

• Current events by tag

• Events by persistence ID

• All persistence IDs

What is the purpose of the 'events by tag' query?

• To query the Journal for deleted events.

• To query events associated with a specific persistence ID.

• To query all events tagged with a specific tag.

• To query the current state of a persistent actor.

In the practical example, which query is used to read events from the account handler persistent actor?

• All persistence IDs

• Events by tag

• Current events by persistence ID

• Events by persistence ID