Orb's billable metrics layer now supports two time-based SQL functions, EARLIEST_BY and LATEST_BY. These can be used in combination with the timestamp of an event to perform queries that take the latest or earliest event in a billing period. They behave as follows:

1. EARLIEST_BY(value_property, time_based_property): Returns the earliest value of value_property ordered by time_based_property.
2. LATEST_BY(value_property, time_based_property): Returns the latest value of value_property ordered by time_based_property.

For example, you might use these functions to compute the earliest and latest storage_gbvalues seen during the month to naively compute storage added. 

Note that Orb automatically applies time range filtering to billable metric queries based on the billing period bounds.