Lambda Destinations: Capturing Failed Async Events for Later Replay

AWS Lambda functions invoked asynchronously by services such as S3, SNS or EventBridge do not return results to the caller, so failures can go unnoticed. By default Lambda retries a failed event twice and then discards it, leaving only a metric and possibly a log entry. The article recommends checking retry behavior and the failure destination for every such function. Lambda destinations can route events that ultimately fail to an SQS queue along with their error message, allowing deliberate reprocessing later. The author notes that destinations do not apply to synchronous invocations or to functions consuming SQS queues, and that functions should be idempotent since duplicate deliveries can occur.