One caveat: Disabling fsyncs can hide problematic access patterns. If you were to e.g. accidentally perform a large set of DML in one-row increments and forgot

One caveat: Disabling fsyncs can hide problematic access patterns. If you were to e.g. accidentally perform a large set of DML in one-row increments and forgot to do so in one transaction, you'd not see a huge penalty in your test environment, but a lot more in production (one fsync for each transaction in the non-concurrent case). Btw, disabling synchronous_commit isn't going to do much once you've disabled fsyncs. What s_c=off basically does is to defer the journal flush to a background process that will do them regularly (unless already done by another session / reason) - but if fsync=off, that's not necessary anyway. And s_c=off does have some small overhead too.