It's also a useful pattern to, instead of configuring the SQS event itself as your Lambda trigger, have a scheduled trigger and then perform health checks on your service dependencies before pulling messages from the queue. This technique saves you wasted retries and even gives you more fine-grained control over deleting messages (the SQS mechanism for saying, "this is done and you don't need to retry it after the timeout). The SQS trigger, in contrast, deletes the entire batch of messages if the Lambda exits cleanly and does not delete any of them if the Lambda does not exit cleanly, which is a bit messy.

Also, you can have an SQS queue subscribe to multiple SNS topics, which means you can set up separate SNS topics for backfill or other use cases. This is especially useful in cross-account use cases, where often your online events are coming from an SNS from a different account, but you want to be able to inject your own testing and backfill events.