This really sounds like you're having an issue linked to the ORM. I don't know the Rails equivalent, but Django's ORM has a way of prefetching related fields o

This really sounds like you're having an issue linked to the ORM. I don't know the Rails equivalent, but Django's ORM has a way of prefetching related fields on a model in a single query. My bet is that your code wasn't 1 query, but actually 4000 * 240 queries, which will always take a while. EDIT: I just saw in a sibling comment that the actual data fetching was only taking 30s. I imagine you were doing that part mostly right