[jiggawatts]

The database engine would have to be designed for this, and/or the clients could request the level of consistency that they require. Most apps only care about “this age or newer”, except when paging through a data set where consistency matters.

E.g.: indexes can include the timestamp and then queries can filter out new rows implicitly. Physically this can be implemented with tiered indexes where the topmost layer is in-memory only and queries older than what it contains are rejected. The on-disk indexes then don’t need old row versions or timestamps.