Unfortunately, KairosDB doesn't do rollups automatically. That sucks, but the performance still works fine for me. Space isn't a issue, Cassandra handles it pretty well. You can set retention policy per data point (TTL) if you need so. If you really need rollups, you can do it manually, saving a query result to a new metric name...

I wasted a lot of time looking for a bulletproof time series db. I found nothing, each one of them have their own set of issues.