Dunno what I'd want to change though.

For anything handling user input I'd be concerned about maintenance status for fixes. Even beyond the codebase itself, even just maintaining an up to date pom.xml can be important - seems theirs was last updated in July of last year. Very brief manual browse of it shows potential exposure to things like https://nvd.nist.gov/vuln/detail/CVE-2022-25647 - not sure if that's reachable in the codebase but there could be others.

Yes, and it was not that well designed to be honest... the successor is quite a lot nicer and it's called Javalin[1].

Same philosophy but just got things right where Spark, being the "first" (in the Java world, using the design inherited by Sinatra[2]) had a few design issues.

[1] https://javalin.io/

[2] https://sinatrarb.com/

That seems to be the status of the whole hadoop ecosystem unfortunately (we're switching away from it at work).

Does the library have anything to do with Hadoop? Are we talking of the same Spark?

https://en.wikipedia.org/wiki/Apache_Spark right? My understanding was it was built on Hadoop (https://en.wikipedia.org/wiki/Apache_Hadoop) infrastructure.

Then it's something else.