Better than POSIX?

That SQLite explanation you quoted is an excellent example. It is worth
noting however that high performance databases can commit a durable
transaction as soon as the necessary journal update has made it to
persistent storage. Nothing else needs to be touched.

SQLite on the other hand, appears to do a checkpoint (i.e. finish the
updates to all the actual data files) as part of every commit. That is not
necessary in a good design. There is nothing fundamental about filesystem
or database design that requires anything except the journal to be
synchronously updated on transaction commit. If durability is not
required, not even that.