Active Record shares all the benefits and drawbacks of ORMs in general. You'll have a much easier time using it if you avoid making these 4 small mistakes.
N+1 queries are quick to sneak in and can wreak havoc on performance. This approach will help you find them quickly, write the test, and preload correctly.
What if we used Active Record to build the query we want for the count of each child record, then used a named scope to nicely place that as a sub-select?
