Event-driven architecture on AWS decouples services, handles traffic spikes, and enables workflows that scale automatically. Here is how to build it correctly with SQS, SNS, EventBridge, and Lambda.
SQS FIFO queues provide exactly-once delivery using a Message Deduplication ID — duplicate messages with the same ID within a 5-minute window are automatically discarded. For standard SQS queues which deliver at-least-once, your consumer must be idempotent — processing the same message twice must produce the same result. Use a DynamoDB conditional write or a unique constraint check as a deduplication mechanism in your consumer code.
SQS is a queue — messages persist until a consumer reads and deletes them, and each message goes to one consumer. EventBridge is an event router — it delivers events to multiple targets simultaneously based on rules, with no persistent storage. Use SQS when you need guaranteed delivery, at-least-once processing, and a work queue pattern. Use EventBridge when you need to react to AWS service events, route events to multiple targets based on content, or trigger scheduled tasks.
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