Let’s say you want to compute avg transaction value of a user in the last 90days. You could pull individual transactions and average during the request time - or you could pre compute a partial aggregates and re-aggregate on read.

OLAP systems are fundamentally designed to scale the read path - former approach. Feature serving needs the latter.

Does Chronon automatically determine what intermediate calculations should be cached? Does it accept hints?

We don't accept hints yet - but we determine what to cache.