Question about socket activiation in systemd

If anyone is knowledgeable about systemd, I’ve been wondering how socket activation works exactly. I get the basic concept; you initialize services that require only a socket from some other service in parallel . Eg, x depends on y, but all it does is write messages to /dev/y, so x can start while y is starting and write those messages. then y will be started and dequeue those messages. But as far as I know, this is a simple local Unix domain socket ( I could be wrong ). So when y does start, and establishes a connection with /dev/y, how does it read past messages in /dev/y? If this is indeed a unix domain socket, one way I can think about is that init intercepts messages to /dev/y, and adds it into it’s own queue. Then when y does start, it writes everything to /dev/y and clears it’s own queue. I feel that this isn’t the right way to implement this though :thinking: