Good question! I don't have any personal experience in that regard. I would probably have paid up for enterprise support (or bought the entire company ;))

I don't how they do it, but the obvious answer is probably sharding. Their cloud costs must be no joke. Peers require tons of memory and I can only guess they must have thousands of transactors to support that workload and who knows how many peers. Add to this that they probably need something like Kafka for integrating/pipelining all this data.

sharding, microservices, they run many instances of Datomic to handle different functionality