I like to keep it simple. I've never been a big fan of most big "mainstream" JVM frameworks like Spring. I much prefer using libraries and writing a small amoun

I like to keep it simple. I've never been a big fan of most big "mainstream" JVM frameworks like Spring. I much prefer using libraries and writing a small amount of glue code to keep it understandable rather than making others become framework competent before hopping on a project. For web services I use Sparkjava but I'm thinking of moving to Javalin or http4k because Sparkjava has really slow release cycles. JSON is either Gson or Jackson. I prefer Jackson just because I know it better but they're both great. I use JDBI for database work but I don't have too much of that in my backend right now. GRPC for cross service communication. Back in 2015/2016 I used Vert.x a bunch but I really didn't like the async programming model. YMMV. Generally I stick to using well known / common libraries written for Java and then later look for a Kotlin version if I have time to dick around a bit. I think this is what I love the most about Kotlin is the great interop with existing Java libraries.