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kotlinlang

I don't think Spring Boot is overkill for anything really. It has been designed for microservices so it's meant to run tiny services with just a few classes. Of course I am not saying you have to use Spring Boot.

For Serverless a Kotliner would be looking at a different lib/toolkit/framework (eg Http4k - <https://www.http4k.org/blog/meet_http4k> ). I don't think Pivotal have a lib covering Serverless development. Pivotal do have their own FaaS platform ( <https://pivotal.io/platform/pivotal-function-service> ) though.