How many times I've had this discussion. Let's publish a notification, and let's have the message receiver call some API. Why not just call the API from the place where you want to publish the message? Because we need this SNS message queue.
Probably because the API can be unreachable, timeout, etc — with a message queues it can be redelivered without permanently dropping customer data or whatever with only a stack trace to remember it by
That's naive without any context to claim. You have to know the source that triggers the code to publish the message, what the message is for, the fault tolerance and availability of the API we're calling before you can even begin to decide. Which you validated perfectly by giving a snarky "what about redundancy" answer to a complicated question.
