[dkwr]

Despite of the question being very unspecific I can’t tell you many details about alternatives. But: I think the biggest ones are Quarkus, Micronaut and Vertx. While Vertx defined itself more as a toolkit.

I never had the chance to try some of these for Production systems or for a proof of concept. This would be really interesting, but I think many companies lean towards Spring, because it is matured, has a big ecosystem and community and stays for so long. And all of this although Spring has a bigger footprint.