java/scala
spring, hibernate, jms, concurrency, akka
netty
mysql, postgresql, mongo, redis, cassandra
hadoop, hbase
tomcat/jetty/glassfish

My recent most interesting tasks:
0) develop and maintain highload scalable microservices based REST API for Internet messenger TangoMe.
1) implement reliable protocol on top of UDP and build it into Netty
2) design and implementation of advertising platform for mobile traffic
3) design and implementation of high performance advertising server
4) design and implementation of high performance advertising statistics aggregation (impressions/clicks data)
5) identify and rank bitcoin arbitrage opportunities between multiple exchanges
6) scrape and aggregate VKontakte data for an in-home project in huuuge volumes
7) and much much more

Please don't hesitate to contact me if you have any questions and for consulting also