Well it depends how much data integrity is worth to you, and how your system works. Every write in postgres is already a transaction - when you can get away with simple crud stuff, often there's nothing to do, you have transactionality already. Transaction isolation levels are where db operation costs might change under concurrent conflicting writes but you can tune that by ensuring single-writer-per-partition or whatever in your server logic and it might add a ms or two. OTOH if you have heavy contestation it can be much more expensive. The performance implications are complicated but can certainly kept to a fraction of overall cost depending on your workload!