I don't have a capture of the CPU figures - it wasn't terrible, but it was unusual. Restarting Kea calmed it down. Recommendations on what to capture if it happens again? The logs don't show anything unusual - just the "Lease File Cleanup" from the prior hour (~40 minutes prior). No related system logs.
Edit: Filling that out a bit, it looked to be eating 100% of one core for >15 minutes. Some sort of race, I imagine.