The key features of mysqlnd_mux are as follows:
Transparent and therefore easy to use:
Supports all of the PHP MySQL extensions.
Little to no application changes are required, dependent on the required usage scenario.
Reduces server load and connection establishment latency:
Opens less connections to the MySQL server.
Less connections to MySQL mean less work for the MySQL server. In a client-server environment scaling the server is often more difficult than scaling the client. Multiplexing helps with horizontal scale-out (scale-by-client).
Pooling saves connection time.
Multiplexed connection: multiple user handles share the same network connection. Once opened, a network connection is cached and shared among multiple user handles. There is a 1:n relationship between internal network connection and user connection handles.
Persistent connection: a network connection is kept open at the end of the web request, if the PHP deployment model allows. Thus, subsequently web requests can reuse a previously opened connection. Like other resources, network connections are bound to the scope of a process. Thus, they can be reused for all web requests served by a process.