Java thread per connection model vs NIO

Question

Is the non-blocking Java NIO still slower than your standard thread per connection asynchronous socket?

In addition, if you were to use threads per connection, would

Answer 1

If you have busy connections, which means they constantly send you data and you send them back, you may use non-Blocking IO in conjunction with Akka.

Akka is an open-source toolkit and runtime simplifying the construction of concurrent and distributed applications on the JVM. Akka supports multiple programming models for concurrency, but it emphasizes actor-based concurrency, with inspiration drawn from Erlang. Language bindings exist for both Java and Scala.

Akka's logic is non-blocking so its perfect for asynchronous programming. Using Akka Actors you may remove Thread overhead.

But if your socket streams block more often, I suggest using Blocking IO in conjunction with Quasar

Quasar is an open-source library for simple, lightweight JVM concurrency, which implements true lightweight threads (AKA fibers) on the JVM. Quasar fibers behave just like plain Java threads, except they have virtually no memory and task-switching overhead, so that you can easily spawn hundreds of thousands of fibers – or even millions – in a single JVM. Quasar also provides channels for inter-fiber communications modeled after those offered by the Go language, complete with channel selectors. It also contains a full implementation of the actor model, closely modeled after Erlang.

Quasar's logic is blocking, so you may spawn, say 24000 fibers waiting on different connections. One of positive points about Quasar is, fibers can interact with plain Threads very easily. Also Quasar has integrations with popular libraries, such as Apache HTTP client or JDBC or Jersey and so on, so you may use benefits of using Fibers in many aspects of your project.
You may see a good comparison between these two frameworks here.