If a contact is joins a workflow too late for a step, this is a sign that the workflow is experiencing throttling.
If you have 34,000 contacts enrolled in a workflow. Your workflow tool processes a minimum of 100 contacts per second, therefore about 6,000 contacts will execute an action per minute. All in all, it will take about 5 minutes and 40 seconds for all 34,000 contacts to execute one action.
Keeping that in mind, let's assume a couple of things:
- All contacts were enrolled today at 3:40 PM.
- The workflow in question is a date-based workflow and the first action is scheduled to execute today at 3:45 PM.
In this case, there will be contacts in this workflow for whom you will see the "Contact joined workflow too late for this step" message because even though they joined the workflow, it took them well over five minutes to execute on the action.
Your workflow may experience throttling if there is a mass enrollment of contacts and the window of execution is too small for contacts to effectively be enrolled and execute on the action in question.