They open at 7am so in the mornings bookings are on the hour. Competitive junior athletes start at 2:30pm shifting to half-hour starts in the afternoon. So they mess up their schedule to accomodate them.
The non-optimal solution is to avoid proposing slots that would create 30m holes. For example do not offer 5pm if a booking ends at 4:30pm. We implemented that but it does not solve the fundamental issue. And they don't want to change. Such is life!
Users are selecting two data points: start time and duration. The fact that those two points have different granularity is what leads to fragmentation, not the fact that start time is more granular than duration.
It is true, however, that more coarse grained allocation sizes will help minimize fragmentation.
emil-lp•40m ago
Eg Braess' paradox, Induced traffic/demand, strategic voting, etc.?