[davidcuddeback]

Sure thing! I'd reframe this as a nearest neighbor search over (start time, duration) tuples. KD trees are what I'm most familiar with for that problem, but there are others that would fit. Check out chapters 1 ("Multidimensional Point Data") and 3 ("Intervals and Small Rectangles") of Foundations of Multidimensional and Metric Data Structures: https://books.google.com/books?id=vO-NRRKHG84C&pg=PR9&source...

R-trees are more generic in that they can store intervals, shapes, volumes, etc, but (start time, duration) tuples are point-like, and that opens more possibilities. The ordered map is going to give you good memory locality. It might be that you'll only beat that when searching for larger durations (that require you to iterate over more of your ordered map). There will probably be an inflection point somewhere, depending on the distribution of your data and queries.

Hope that helps!