Event sourcing pattern in Kafka - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the Event Sourcing Pattern?

Event Sourcing is a design pattern where all changes to application state are stored as a sequence of events. Instead of saving just the current state, you save every change that happened, so you can rebuild the state anytime by replaying events.

intermediate

How does Kafka help implement Event Sourcing?

Kafka acts as an event store by storing events in topics. Each event is a message in Kafka, which can be replayed to rebuild the state or to trigger other actions. Kafka's durability and ordering make it ideal for event sourcing.

intermediate

What is an aggregate in Event Sourcing?

An aggregate is a cluster of domain objects that can be treated as a single unit. It helps organize events and ensures consistency when applying changes.

beginner

Why is replaying events important in Event Sourcing?

Replaying events means applying all stored events in order to rebuild the current state of an entity. This allows recovery from failures and supports auditing by showing how state evolved over time.

advanced

What is a common challenge when using Event Sourcing with Kafka?

One challenge is handling event versioning. As the system evolves, event formats may change. You need strategies to handle old and new event versions to keep the system working smoothly.

What does Event Sourcing store in Kafka?

A A sequence of events representing all changes

B Only the latest state snapshot

C User login credentials

D Database schema definitions

Event Sourcing stores every change as an event, so Kafka holds a sequence of these events.

Why is Kafka suitable for Event Sourcing?

A Because it automatically deletes old events

B Because it only supports real-time data

C Because it stores events durably and in order

D Because it encrypts all messages by default

Kafka keeps events durable and ordered, which is essential for replaying events correctly.

What is the purpose of replaying events in Event Sourcing?

A To rebuild the current state from past changes

B To delete old data

C To speed up database queries

D To send notifications to users

Replaying events applies all changes in order to reconstruct the current state.

What is an aggregate in Event Sourcing?

A A database index

B A group of related events representing one entity

C A type of Kafka topic

D A user interface component

An aggregate groups events that belong to the same entity or concept.

What problem does event versioning solve?

A Filtering events by user

B Encrypting events for security

C Compressing events to save space

D Handling changes in event formats over time

Event versioning manages how to handle old and new event formats as the system evolves.

Explain how Event Sourcing works and why Kafka is a good fit for it.

Think about saving every change and how Kafka keeps messages.

Describe the role of aggregates and event versioning in Event Sourcing.

Consider how events are organized and how changes over time are managed.