I've been thinking about converting a legacy application which uses UUIDv4 to use ULIDs instead going forward, but then to represent these ULIDs in a format that is compliant with a UUIDv4. I have not thought through the possible downsides, but I think it should be a pretty straightforward change. Of course old records will remain true random UUIDv4s, but at least new records will be time-order and as such will create less stress on the B-Tree index when writing them.