In a typical messaging app (e.g. Signal) clients connect to a single conceptual "server" (typically load-balanced) which directly routes messages to other clients. This means the server knows the to and from of every message (its metadata), even if use of end-to-end encryption prevents seeing the actual message content. In contrast, RACE has an entire network of independent servers that use special multi-party computation (MPC) algorithms to route messages without individual servers learning the metadata.