Hi!
I'm a very experienced Java developer and this is what i do on my regular job, i develop server side java apps ( spring, Hibernate, Quartz, etc.). Anyways what you need is a distributed hashmap like Hazelcast ( not free for more then 2 instances for enterprise solutions) or Infinitispan to share session across instances. This is pretty straight forward solution but it takes time to make. Please contact me with more details and requirements.
p.s. I can start immediately.
p.p.s I looked at the code, this is not simple java .. it's Scala ( there's a difference ) and it uses Play framework. I can do this both.
Regards,
Ivan R.