So Amazon has created a new calling convention, where conditional logic now also requires a context switch and JSON serialization. Then they charge you for the call .. $tdcall?
This will certainly have some useful applications, maybe someone will build an inexpensive data processing pipeline on top of it. Having seen many visual workflow tools through the years, most are simplifying complex underlying process, but these step functions and state transitions are modeling basic internal control flow with complex abstractions and little benefit other than retries with backoff.
The pure functional immutable nature of the data flow is ideally nice but tainted by the JSON. The parallelism is interesting, but it seems bolted on instead of a more powerful central part of the design.