It is possible to configure event loop with NettyStreamFactoryFactory but there is no way to configure socket channel type.

In case when I want to use native transport in my Netty server-side application I have to use EpollEventLoopGroup. Also I want to share event loop between my server request handlers and Mongo driver to reduce threads count and context switches between them. Netty maintains compatibility between event loop and channel implementations and don't allows to mix different types in bootstrapped server or client. So I have to create separated NioEventLoopGroup for Mongo driver because channel type currently is not configurable.