Scala with Akka, and RabbitMQ for scaling across multiple servers. This would be a bit more work up front than a web framework like Django but it would be more

Scala with Akka, and RabbitMQ for scaling across multiple servers. This would be a bit more work up front than a web framework like Django but it would be more maintainable in the long run due to the fact that Akka encourages writing simple loosely coupled code that does one thing (Single Responsibility Principle). Even more important is to get the dev team working using TDD (Test First Development) and provide a proper vision to guide them. Things like Uncle Bob's Clean Code book, and the raw, original Agile manifesto before it got sucked into the Scrum and XP methodology machine. Even though the code is more functional than object-oriented, the SOLID principles still mostly apply. Some alternate choices that could be OK if you can find at least one good developer to lead the team, are Clojure, or Erlang/Elixir. With the Erlang virtual machine, RabbitMQ would not be necessary, although I like it because it gives you a lot of points where you can measure/monitor the internals of your application. I would also seriously look at adding Apache Camel to the mix even though Akka does not require Camel to integrate actors. But Camel is a thin layer that makes it easier to reconfigure integration points.