I remember working at a company where we had a backend web framework that was essentially a DAG. You could use it to create API's where the caller simply specifies what they want, and the server figures out, through graph theory, what series of processing steps and API calls to other services should be performed (some of which can have dependencies on the results of other API calls and/or processing steps), and the optimal way to parallelize them.

It struck me as being both a very intriguing framework, and also exceptionally over-engineered for the kind of problem it was solving (since an async-await architecture gets you all the same benefits).