Andy Brownsword performs several probes:
Specifically we’ll use a binary search approach to narrow the search range. We abuse the correlation between the clustering key and timestamp to zero in on the records, using the key for navigation, and the timestamp to guide us.
We’ll start with the first and last records as boundaries, followed by checking the timestamp at the mid-point. Depending on whether the timestamp is before or after our target point in time, the appropriate boundary is moved. This halves the key space, and the search repeats until we’ve narrowed the range sufficiently to scan a very small portion of records.
It’s a neat idea, though do watch for Andy’s warning at the end.