many-to-many: store and query

[lament forum]

I have a use case where there are about 60 possible choices, and each user can select between 1–60 of them.

Currently I’m storing them in a separate join table like:

{ userId, choiceId }

This works for filtering (e.g. “find users who selected X”), but with 10k users it could mean 100k–600k+ rows, which feels heavy.

I’m considering other approaches:

Store choice IDs in an array inside the user document. (But then how to query efficiently by choice?)

Use a bitmask (60 choices = fits in a 64-bit int) for compact storage. But Convex doesn’t seem to support bitwise queries directly.

A hybrid approach — store array/bitmask in the user doc for compactness, and maintain a separate index table for filtering.

What’s the recommended way in Convex to store and query this kind of many-to-many preference data efficiently?

[fathom thicket]

Thanks for posting in #1088161997662724167.
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