How to create a search api facet for filtering user access

I’m trying to figure out how to create a search api facet, that will filter results based on user access. By default, I’m bypassing access check hence showing all the nodes. I need to add a checkbox, which will filter results by access for current user (showing only already purchased items).
One approach could be perhaps indexing all accessible nodes per user (about 300 nodes and 4000 users at the moment) similarly to flag_search_api or another and likely more elegant solution, adding access check to query if the access checkbox is selected.
Does anyone have any idea if the latter would work and how to actually implement it?

Thanks.