Asynchronous processing with SQS

Comments

• The queue decouples request intake from processing. If Lambda is slow or fails, messages wait in SQS instead of being lost.
• The dead-letter queue (DLQ) receives messages that fail repeatedly, so you can review them without blocking the main queue.
• SQS Standard delivers each message at least once and does not guarantee order. If order or deduplication matters, use SQS FIFO.
• Lambda can use reserved concurrency so it does not overwhelm the database or downstream services.

Information flow

1. Amazon API Gateway

   The client sends the request to API Gateway.

2. Amazon SQS

   API Gateway puts the message in the queue and responds without waiting for processing.

3. AWS Lambda

   Lambda consumes messages from the queue in batches and runs the business logic.

4. Amazon DynamoDB

   Lambda stores the result in DynamoDB.

5. Amazon SNS

   Lambda publishes an event to SNS to notify subscribers, such as email or HTTP endpoints.

6. Dead-letter queue

   If a message fails more times than allowed, SQS moves it to the DLQ for review.