Promising efficiency, "new functionality written in Rust".

But also:

> Available under a commercial license, Synapse Pro will alhelp fund and accelerate the continued open source development of Synapse for the benefit of all of Matrix.

https://mastodon.matrix.org/@element/113627636666252355

> Synapse Pro is for nation-scale deployments, not community use.

https://mastodon.matrix.org/@element/113628266288510356

Not sure how to feel about it just yet.