CQRS pattern in Kafka - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does CQRS stand for?

CQRS stands for Command Query Responsibility Segregation. It means separating the part of a system that changes data (commands) from the part that reads data (queries).

beginner

In CQRS, what is the role of commands?

Commands are requests to change data. They tell the system to do something, like add or update information. Commands do not return data, only success or failure.

intermediate

How does Kafka help implement CQRS?

Kafka acts as a message broker that transports commands and events between services. It helps keep the command and query sides separate and syncs data changes through event streams.

intermediate

Why separate read and write models in CQRS?

Separating read and write models allows each to be optimized independently. Writes can focus on data integrity, while reads can be fast and scalable, improving overall system performance.

beginner

What is an event in CQRS and Kafka context?

An event is a record of something that happened, like 'OrderPlaced'. In Kafka, events are messages sent to topics that other parts of the system listen to and react upon.

What is the main purpose of the 'Command' in CQRS?

A To change data in the system

B To display data to users

C To store data permanently

D To request data without changing it

Commands are used to change data, like creating or updating records.

In CQRS, which side handles queries?

A Query side

B Command side

C Both command and query sides

D Neither side

The query side handles reading data without changing it.

How does Kafka support CQRS architecture?

A By storing data in databases

B By replacing the query side

C By directly updating user interfaces

D By sending commands and events as messages

Kafka sends commands and events as messages to keep command and query sides in sync.

Why might you want to separate read and write models in CQRS?

A To combine all logic in one place

B To make the system slower

C To optimize each model for its purpose

D To avoid using events

Separating models lets you optimize writes for consistency and reads for speed.

What is an event in the context of CQRS and Kafka?

A A command to change data

B A message describing something that happened

C A database query

D A user interface component

Events describe things that happened and are sent as messages in Kafka.

Explain the CQRS pattern and how Kafka can be used to implement it.

Think about how commands and queries are handled separately and how Kafka moves messages between parts.

Describe the benefits of separating read and write models in a CQRS system.

Consider why different parts of a system might need different designs.