Is there something like Datomic for Postgres? Having your team learn clojure, datalog, deploying Datomic was a huge pain for us. Not the road we recommend since all we really needed were just immutable append only log of all transactions.
Now days it's far better to look at tooling outside and around Postgres to give you that. Under the covers WAL is effectively this, so with tools like backrest you can maintain backups and WAL forever then have ability to restore and old point as you see fit. On managed service providers a lot of them give this out of the box though only for a limited period of time.