Follow-up from "Make DAP Free tier available on self-managed"
The following discussion from !228648 should be addressed:
- [ ] @a_akgun started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/228648#note_3217535819):
> We may consider: `where(ultimate_only: true).pluck(:reference).to_set`
>
> Also is it too big for the memory in any scenario?
issue