Until you reach 10B datoms and then you're off for a fun ride sharding with multiple databases. Also in an IoT context or more general timeseries usage you very likely don't care about tx, but very much do about write throughput and not having a spof, which Datomic isn't good at at all.

Datomic is an ok choice in some contexts, but the one detailed here is not one of them, you're likely to reach Datomic limits quickly and be in a world of hurt when you do.