Event-Driven Architecture for Java Developers

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Summarize the following topics:

• THE DUAL-WRITE DILEMMA Frequently microservices need to update two separate systems. Eg. Database + Message Queue

This is known as the Dual-Write problem. It is a potential source of inconsistency.

Avoid the Dual-Write problem using a Transactional Outbox.

• See how CockroachDB's Change Data Capture can simplify your implementation

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The Dual-Write Problem: It occurs when two independent systems need to be updated in a transactional manner.

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• Delivery Guarantees

Using the Transactional Outbox Pattern allows us to guarantee that every message will be published: At least once

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Building systems of events is advantageous because:

• They are more resilient to failures.
• They are easier to distribute and scale.
• They are loosely coupled.

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Messages come in three types:

• Commands, Commands are a request to change the state.
• Queries, Queries request information about the state.
• Events, Events record the changes to the state. Represent something that happened in the past (a fact).

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Outbox Table

• Outbox Table should be named based on what kind of data it contains
• minimal set of columns we want for our table: Unique Id, Timestamp, Event Type, Event Data