Domain Consistency in Event-Driven Architectures
Publication date: March 8, 2022 (Diagram history)
This architecture shows how to increase the resilience of your event-driven architecture by applying the transactional outbox pattern to your domain's database transactions. You ensure that all local changes raise a corresponding domain event that other domains can project, enabling eventual consistency across bounded contexts.
Domain Consistency in Event-Driven Architectures
The following steps describe the architecture:
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To support event choreography between your domains, set up a custom event bus using Amazon EventBridge.
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Detect changes on your monolith's relational database by setting up change data capture (CDC) with AWS Database Migration Service (AWS DMS) and Amazon Kinesis Data Streams.
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Create an outbox table to insert events 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).
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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.
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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 queue, then handle them with a Lambda function and an Amazon SQS dead-letter queue (DLQ).
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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.
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On your microservices, repeat the same transactional mechanism around both entity tables and the event outbox table.
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Capture the inserts on the event outbox table using DynamoDB Streams.
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Handle the data stream with a Lambda function, publishing the inserts as domain events in the event bus.
Further reading
For additional information, refer to the following resources:
Diagram history
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| Change | Description | Date |
|---|---|---|
Initial publication | Reference architecture diagram first published. | March 8, 2022 |
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