Matrix is a new message-oriented data synchronization middleware,
used as a federated platform for near real-time decentralized applications.
It features a novel approach for inter-server communication
based on synchronizing message history by using a replicated data structure.
We measured the structure of public parts in the Matrix federation
as a basis to analyze the middleware's scalability.
We confirm that users are currently cumulated on a single large server,
but find more small servers than expected.
We then analyze network load distribution in the measured structure
and identify scalability issues of Matrix' group communication mechanism
in structurally diverse federations.