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Guneet Nagia
Guneet Nagia

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Seamless Database Migration in a Microservices Architecture: Cloud-Native, Event-Driven Strategies

Downtime during a database migration can tank a production app—trust me, I’ve been there. As a solution design, I tackled this head-on, designing a cloud-native, event-driven solution using Kafka, AWS, and microservices. Stick around to see how I replaced DynamoDB with MongoDB without breaking a sweat.

Here’s how I tackled this at scale: a phased, zero-downtime migration using AWS, Kafka, and event-driven microservices. Check out this diagram for the flow:

The approach introduces an abstraction layer between services and databases, leveraging Kafka for event-driven reliability. Here’s how it works:

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Phase 1: Current State

Data Flow:

  • The Writer Service writes data to Amazon DynamoDB.
  • Reader Services fetch data from DynamoDB.
  • Archival Service moves older data to an Amazon S3 Bucket for storage.

Retention Policy: Data in DynamoDB is retained for 15 days before archival.

Phase 2: Transition (Dual Write & Validation)

Data Replication:

  • Introduce a Kafka Sink Connector to sync data from Writer Service to MongoDB.
  • Continue writing to DynamoDB while also storing data in MongoDB.

New Archival Process:

  • A new S3 bucket is created to store data from MongoDB.

New Service Introduction:

  • A New Service API is introduced to provide the same responses as the existing database.
  • A toggle flag is implemented in the API to switch between DynamoDB and MongoDB.

Validation Steps:

  • Validate responses from New Service against existing Reader Services.
  • Ensure consistency in both S3 archival processes.

Phase 3: Full Migration & Decommissioning

Switching Data Source:

  • Change the toggle flag to make Reader Services fetch data from MongoDB.

Enhancements & Optimization:

  • Fully transition reading services to the New Service.

Decommissioning Old Infrastructure:

  • Decommission DynamoDB and remove dependency on the old archival process.

Final Validation & Completion:

  • Validate that all data is successfully migrated and all services function as expected.

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