If you need in memory multi column (non key) lookups you’re going to start making things pretty complex. No matter what you do, if you want to avoid linear scans you’ll need to maintain secondary indices. Adding in mnesia won’t really change that, or even something fancy like an in memory sqlite table.
15k items isn’t really all that many. You could easily just have 1 table for canonical key → value pairs, and then N tables, one per column you want to query on, containing value → canonical key pairs.
