I did one of these after a long day spent deep in the guts of the web framework (Elixir/Phoenix) trying to optimize performance under DDOS on an ad-tech system.

I did one of these after a long day spent deep in the guts of the web framework (Elixir/Phoenix) trying to optimize performance under DDOS on an ad-tech system. They gave me a codebase with a "REST" API for their mobile client that had some problems and wanted me to spend "4 hours" adding features to it and fixing any problems that I saw. I made the changes, then told them that the biggest problem was that their REST API was just ad-hoc JSON over HTTP, with ill-defined data and poor error handling. I recommended using GraphQL, which defines the over-the-wire format and error handling, reduces network round-trips, and is "self-serve", avoiding many meetings between front-end and back-end people and increasing dev velocity. This was too much for them, as they were expecting some changes to put lipstick on the pig. I said that there were other REST-based frameworks that would add standard structure (e.g. JSON API) and support introspection with e.g. OpenAPI. I got rejected because I "didn't have enough experience with the framework", and "it didn't seem like a good fit". Their "seniors" doing the interviewing were not able to build a system that worked before they ran out of money, and they are now out of business.