[esseph]

How small is small, and how often is that state checked?

I guess it's probably not tracking tons of IDs like tracking packet state through a network device.

Even a few million (max) UUIDv4 is probably fine then, yeah?

[SahAssar]

Yeah, I'd say that sounds fine. Since these are supposed to be used within a short time it'd also be easy to cleanup unused ones more then 5mins old or so.