When a MongoDB server accepts a proxied connection, it needs to read and process the first special "proxy packet" coming on the connection. Now these reading and processing are executed on the same thread as the one accepting new connections. Executing all these operations on a single thread creates a bottleneck that limits the server's ability to open multiple clients' connections in a short period of time.

If we move reading and processing "proxy packet" to the connection thread, this will allow to do this work concurrently on multiple threads and better utilize available resources. As a result, the server will be able to open more clients' connections in a short period of time.