In this case, they probably should have used Step Functions Express, which charges based on duration as opposed to number of transitions and they're looking for "on host orchestration" like orchestrate a bunch of things which usually are done in small time and are done over & over many times. Step functions is better when workflows are running longer, and exactly once semantics are needed. Link for reading differences between Express & standard step functions: https://docs.aws.amazon.com/en_us/step-functions/latest/dg/c....
This also exemplifies the fact that I learned while being at Amazon & AWS that Amazon themselves dont know how best to use AWS. This being one of the great examples. I'll share 1 more:
- In my team within AWS, we were building a new service, and someone proposed to build a whole new micro service to monitor the progress of requests to ensure we dont drop requests. As soon I mentioned about visibility timeout in SQS queues, the whole need for the service went away. Saving Amazon money ($$) & time (also $$). But if I or someone else didn't mention, we would have built it.
I dont think serverless is a silver bullet, but I don't think this is a great example of when not to use serverless. It helps to know the differences between various services and when to use what.
PS: Ex Amazon & AWS here. I have nothing to gain or lose by AWS usage going up or down. I'm currently using a serverless architecture for my new startup which may bias my opinions here.