The heart of Functions as a Service is, of course, the function. In Amazon Web Services, these are deployed using the service AWS Lambda. That's not the only AWS feature we'll use, as we've already mentioned. Once we have a function, we need a way to execute it. This is done via one or more triggers, and the function itself has tasks it needs to perform, so we'll demonstrate more service usage via API calls when we finally write the function.
It might be helpful at this point, given that our application is structured significantly differently than anything else we've looked at, to look at a system diagram:
Here's the rough flow:
- A message is published to a topic in the Simple Notification System
- Once the permissions of the caller have been verified, the message is delivered
- Upon message delivery, a trigger is fired, delivering the message from the topic to our function
- Inside the function, we'll query Amazon's DynamoDB to get the list of recipients that have signed...