Are there any Datomic-like query layers on top of Postgres for approaches like this where you're recording immutable occurrences rather than updating mutable records?
No, this would be more be about using different ways of mapping data to the database from an applications point of view. So for an developer it would increase the load a tad in terms of exploring data when debugging simple things.
On the other hand, the increase in exploration costs should be more than offset by having most data changes logged to be able to track changes.
