Heap is an analytics company that stores all (json) events automatically and then provides real-time queries. Their business sustainability is directly tied to how effectively they store and query this data.

They solve it with a large cluster of Postgres server running fast disks with partitioning handled by the Citus extension, along with several low-level tweaks.

RDS does not support these scales or any clustering. Aurora does not have parallel processing. Redshift would be fast but is very expensive and does not have the same level of Postgres features.

There is Citus Cloud so you can get close to Heap's setup with Citus maintaining it all, but that gets pricey too.