Yeah, it looks like I got that part wrong. (I intentionally skimmed over the transactor, because I was avoiding "how" issues and because my understanding of it wasn't that clear.)
The transactor is involved in just writes, not reads. (So that helps.) It's not distributed and cannot be distributed, in this system, because it ensures consistency, so yes, it is potentially a bottleneck. In blog comments by Rich Hickey[1], he states:
"Writes can’t be distributed, and that is one of the many tradeoffs that preclude the possibility of any universal data solution. The idea is that, by stripping out all the other work normally done by the server (queries, reads, locking, disk sync), many workloads will be supported by this configuration. We don’t target the highest write volumes, as those workloads require different tradeoffs."
Presumably, 1) the creators of Datomic think that performance can be good enough to be useful, 2) this is a new model that probably requires testing to prove is practical.
Huh? How is that consistent with:
> access the data storage through a new distributed component called a transactor.
If "doing the transactions" consists of more than passing out incrementing transaction tokens, won't the transactor be a bottleneck?