How to force Power Automate to run a single instance of a Flow triggered by SharePoint

Recently I created a Flow to process items added to a SharePoint list as they are created.

I needed each item to be processed on a 'round robin' basis, i.e., one at a time, to ensure an allocation algorithm worked fairly. I needed to prevent parallel runs of the Flow.

However, in my testing, I was adding lots of items to the list at the same time, and I ended up with Flow runs with timestamps looking like this ...

.... i.e., everything was being processed at the same time, and skewing my round-robin processing.

I started thinking about how to resolve this, thinking of complex locking mechanism etc, then it dawned on me - there's a setting IN the Flow Connector which does this!

Simply go to your Trigger Action settings, and turn on Concurrency control, and set it to 1 as shown below:

forces Power Automate to process one trigger event at a time, queueing the res ... this little setting forces Power Automate to process one trigger event at a time, queueing the rest!

... notice the new 'Waiting' Status, showing requests that are queued - only one request is allowed to run at any given time.

Nice!