API Gateway direct integration to Step Functions. Unlike Lambda, there is not automatic transform for requests so I just wrote one and copy/paste it to each method integration (via a preprocess script; one of the ugly bits). Yes, EXPRESS state machines. I’ve found they have better tail latency behavior, and of course they involve zero patching/dependency updates which is nice.
The state machines use JSONata for the sweet, sweet power vs JSONPath. Generally I have a Parallel state that splits the different parts of the page and Map states for data driven repetition (usually some data pulled from DDB). I have a simple JSONata method for replacing placeholder values (aka data binding). Zero Lambda at the cost of come copy paste.
I’m not unhappy with it despite the warts.
Thanks for replying, that's an interesting architecture. The idea of using a high-up parallel state seems particularly neat as a way to ensure every part of the page render stays independent, and to burst up the compute serving the response.