With the following code in a custom java action you can create a wait action. The input parameter is a long value indicating the time to wait in milliseconds.
// BEGIN USER CODE
Thread.sleep(timeInMs);
return true;
// END USER CODE
I do however think that the issue that you are experiencing is not due to the speed at which the records are created and there is another cause. Maybe you can share the microflow and explain the model to get an answer for your issue that solves the problem correctly.
Do you commit in a loop?