Hello Sir.
I'm founder of Devster Lab outsource company. We specialize on development websites with rich user interface and functionality. In devster Lab you can find developers with all experience you have mentioned.
I have a team of qualified professionals each of which is a master of his craft.
Frontend develoopers specialize on Bootstrap, React, Redux and AngularJs.
Backend developers are masters in Java, node.js and different databases like Mysql, Postgress, Cassandra, MongoDB.
Thanks for attention. Hope my propothition is interesting for you.