Earliest event-time boundary at which the Feature may emit an output. This gates outputs, not
the historical inputs read by a window. For example, a 365-day window with
start_time=2026-01-01 begins emitting partial-window values on that date instead of waiting
for 365 days of data; a lifetime window produces no output before start_time. If unset,
tumbling and fixed-duration sliding windows first emit at an offset-aligned boundary after a
full window can be formed. If unset, lifetime sliding windows and rolling windows emit as soon as
eligible source data exists.
Not currently supported for sawtooth windows or for Features with a stream source.
Earliest event-time boundary at which the Feature may emit an output. This gates outputs, not the historical inputs read by a window. For example, a 365-day window with start_time=2026-01-01 begins emitting partial-window values on that date instead of waiting for 365 days of data; a lifetime window produces no output before start_time. If unset, tumbling and fixed-duration sliding windows first emit at an offset-aligned boundary after a full window can be formed. If unset, lifetime sliding windows and rolling windows emit as soon as eligible source data exists. Not currently supported for sawtooth windows or for Features with a stream source.