Race condition when using slapo-unique?

Hi, I am using OpenLDAP 2.3.43 with BDB 4.5.20 and recently encountered a problem where two different entries were created with the same mail attribute value. The problem is that the mail attribute was defined as unique in slapd.conf: index mail eq,sub overlay unique unique_attributes mail

The two similar entries were created about 300 milliseconds apart. To add to the confusion, an ldapsearch for the same mail value occurred at roughly the same time.

So far I have not been able to reproduce this, which indicates that it is a race condition.

I hope someone can help me, or direct me to some documentation.

Regards, Magne Land