Seamless queries that span different storage layers is a pretty big deal. This is like having a table with new data in RDS and old data in Athena. The potenti

Seamless queries that span different storage layers is a pretty big deal. This is like having a table with new data in RDS and old data in Athena. The potential downside is unpredictable query performance. For example, suppose you have a query that calculates daily statistics from your time series data. The query takes 1 second to execute when you run it for yesterday's data, but 1 minute to run for a day six months in the past, because you've inadvertently shifted your work onto the slower storage layer.