Play Framework

Play Framework is a web framework for Java and Scala, described as high velocity and built on a lightweight, stateless and web-friendly architecture. Versions 3.0 and 2.9 are maintained in parallel, with separate Java and Scala documentation, a discussion forum, a Discord server and published case studies.

Being stateless is the architectural decision everything else follows from. Holding no session state on the server means any instance can serve any request, so scaling is a matter of adding instances rather than coordinating them, and an instance failing costs nothing but the requests in flight. That is the correct design for anything running behind a load balancer, which is now almost everything.

Supporting Java and Scala equally is unusual and it reflects where the framework came from. Scala teams gain a mature web layer and Java teams gain a framework designed around reactive principles rather than retrofitted with them, and both sets of documentation are maintained rather than one being a translation.

Maintaining two versions in parallel is worth understanding before adopting. It suits existing users, and a new project should establish which line is receiving feature work rather than assuming the higher number is the default.