Facebook maintains a patch-set, not a full fork. They still track Oracle's releases and apply their patches on top. Facebook definitely has the resources to mi

Facebook maintains a patch-set, not a full fork. They still track Oracle's releases and apply their patches on top. Facebook definitely has the resources to migrate to Postgres, if there was any motivating reason to do so. Indeed, Facebook developed their own LSM-based key-value store (RocksDB) and MySQL storage engine based on it (MyRocks) and then migrated the majority of their db fleet to that. In total that's massively more work than migrating to Postgres would have been. Part of the reason was that MyRocks provides better compression than pretty much any other possible choice, and that adds up to an astronomical amount of cost savings at Facebook's scale. In contrast, what would Facebook have gained from moving to Postgres instead?