It's rather simple, just messy to look at. It's a timer that triggers a cluster that processes raw data files and uploads the JSON to a server with a reliable file system. Then a Lambda function processes API requests to read that JSON and serve a response.

"Lock-in" is just a trade-off like any other engineering decision, same as what programming language or API schema you choose. AWS is massive and reliable, and these services are cheap and widely available so I don't see much of an issue here.