Event-Driven Architectures

Increase the resilience of your event-driven architecture by applying the transactional outbox pattern to your domain’s database transactions, ensuring that all local changes raise a corresponding domain event that other domains can project.

• To support event choreography between your domains, set up a custom event bus using Amazon EventBridge.

• Detect changes on your monolith’s relational database by setting up change data capture (CDC) on the database with AWS Data Migration Service (AWS DMS) and Amazon Kinesis Data Streams.

• Create an outbox table to insert events to be published following any database change, and wrap the write of both entities and outbox tables inside a transactional operation with atomicity, consistency, isolation, and durability (ACID).

• Capture the inserts in the outbox table using an AWS Lambda function listening to the Kinesis CDC stream, and publish them as domain events in the event bus.

• On your context bounded microservices, capture the relevant external events by setting up a rule in EventBridge to push them into an Amazon Simple Queue Service (Amazon SQS) queue, then handle them with a Lambda function and an SQS dead-letter queue (DQL).

• Use the incoming external domain events to build eventually consistent projected representations of those other domains’ databases, implemented with Amazon DynamoDB tables, for local logic to read.

• On your microservices, repeat the same transactional mechanism around both entity tables and the event outbox table.

• Capture the inserts on the event outbox table using the DynamoDB data stream.

• Handle the data stream with a Lambda function, publishing the inserts as domain events in the event bus.