Unix Domain Sockets are the standard mechanism for app->sidecar communication at Google (ex: Talking to the TI envelope for logging etc.)
Search around on Google Docs for my 2018 treatise/rant about how the TI Envelope was the least-efficient program anyone had ever deployed at Google.
servo's Ipc-channel doesn't use Unix domain sockets to move data. It uses it to share a memfd file descriptor effectively creating a memory buffer shared between two processes