Hi @sanjay-optiv,
Due to the multi-threaded processing of IDN, you cannot guarantee a unique ID or a sequential ID for all the users when you create multiple users at the same time.
The data should exist in the system first, for the uniqueness check to work. Due to the parallel processing, it becomes impossible for IDN to accurately check this.
Here is a similar thread :
You may want to look into other options instead of incremental account ID’s or the suggestion put forward in the above thread.