That's a great post. This is exactly the use-case we have, with a type property.
Regarding the usage of mixed indexes -
- I'm less concerned with property updates in this case (as opposed to "inserts"), as the type / label of a vertex won't change.
- However, I've seen cases in the past, where queries relying on a mixed index fail while the index backend still hasn't caught up to the storage backend. I'm guessing there's no way around that?

For another approach, how about cleanups / ttls / etc. ?
Assuming the business model can sustain this, is there a way to compute for a specific vertex label, what will be the upper bound for the number of vertices?