That means another trade was going through at the same time and it took a while.  The engine takes out exclusive locks on any action that can modify the state of each individual security.  (eg, making a bid/ask order, exercising an option, etc.)

I've cleared out most of the performance issues around the bitcoind.  I think we now have two situations that cause this:

1) Lots of traffic.
2) I suspect it may happen when the db is getting backed up.  The db dump takes out read locks.  I'm hoping to address this soon by setting up db replication, then doing the backups on the replica.

Cheers.