Datomic’s single-writer system requires conditional put (CAS) for index and (transaction) log (trees) roots pointers (mutable writes), and eventual consistency for all other writes (immutable writes) [0].
I would go as far as saying a FoundationDB-specific Datomic may be able to drop its single-writer system due to FoundationDB’s external consistency and causality guarantees [1], drop its 64bit integer-based keys to take advantage of FoundationDB range reads [2], drop its memcached layer due to FoundationDB’s distributed caching [3], use FoundationsDB watches for transactor messaging and tx-report-queue function [4], use FoundationDB snapshot reads [5] for its immutable indexes trees nodes, and maybe more?
Datomic is a FoundationDB layer. It just doesn’t know yet.
[0] https://docs.datomic.com/on-prem/acid.html#how-it-works
[1] https://apple.github.io/foundationdb/developer-guide.html?hi...
[2] https://apple.github.io/foundationdb/developer-guide.html?hi...
[3] https://apple.github.io/foundationdb/features.html#distribut...
[4] https://docs.datomic.com/on-prem/clojure/index.html#datomic....
[5] https://apple.github.io/foundationdb/developer-guide.html?hi...
That sounds a lot like Datomic's "Storage Resource" approach, too! Would Datomic-on-FDB make sense, or is there a duplication of effort there?