re concurrent writes: The issue we ran into was deadlocks when we upserted batches of records within a transaction. E.g. transaction A updates row 1 then row 2

re concurrent writes: The issue we ran into was deadlocks when we upserted batches of records within a transaction. E.g. transaction A updates row 1 then row 2 and transaction B updates row 2 then row 1. If you sort so that you update rows in the same order across all transactions, then it won't deadlock. E.g. sort records by primary key and then upsert. If you can't do that, then advisory locks seems like a good idea.