Our current approach is to make code search available for Bronze/starter and above.
We appreciate your feedback on enabling it for non-paid.
This is the Epic we are working on, feel free to leave feedback here as well.
https://gitlab.com/groups/gitlab-org/-/epics/1736
Although not at GitLab.com scale, I've worked on a few search-related projects (often using Elasticsearch) in the past and would consider offering some ideas.
Does GitLab have a policy for attribution/licensing of technical design input from external contributors? (this is partly out of curiosity in general -- I don't know for sure whether I'd have anything to add that your team wouldn't already have thought of themselves)