> having the ability to scale the coordinator past a single machine

Since Citus v11 (released 4 years ago), any worker node can also work as a "query router" (a node that you can query against [1], and works from this perspective as a pure coordinator:

> for very demanding applications, you now have the option to load balance distributed queries across the workers

You can also setup such query routers as dedicated nodes by setting the `shouldhaveshards` to `false`, becoming an effective coordinator (for querying; not for metadata operations).

So with Citus you can absolutely have as many query routers (coordinators if you wish) as you want.

[1]: https://www.citusdata.com/updates/v11-0/#metadata-sync

Edit: formatting, typo