SQLite would cut it just fine. Though it would also need an extension like this one, if you'd want the signature verification and hashing to happen inside SQLit

SQLite would cut it just fine. Though it would also need an extension like this one, if you'd want the signature verification and hashing to happen inside SQLite. The difference between SQLite and Postgres would be that more than one client can connect over the network to PG (or most any other sql db out there really), while SQLite is meant to be embedded, which, if you already have LevelDB working (as is the case in Bitcoin Core), wouldn't be all that different.