The Gotchas: When to Hold Your Horses (Avoid Parallelism)
So, we've established that parallel branches are great for speed, but they aren't a universal solvent for all your flow problems. There are critical scenarios where forcing parallelism will lead to chaos, errors, and tears (of frustration, mostly).
The number one reason to avoid parallel branching is **data dependency**. If Branch B needs a piece of information (like an ID, a status, or a calculated result) that is *only* generated by an action in Branch A, you simply cannot run them in parallel. If you try, Branch B will fail because the data it expects hasn't been created yet. This seems obvious, but it's the most common mistake when implementing this feature.
The Danger of Concurrent Writes and Race Conditions
Another massive red flag is **concurrent writes to the same record**. Imagine both Parallel Branch A and Parallel Branch B are trying to update the *same* line item in a SharePoint list or the *same* row in a SQL database. Which one gets there first? Which one's changes stick? You've just introduced a **race condition**. The outcome will be unpredictable, and debugging it will be an absolute nightmare.
If you must update the same data store twice, you need a sequential process to ensure the updates happen in the correct order. For example, if Branch A adds a 'Date Approved' and Branch B adds a 'Final Comment,' you need to decide which update takes priority or combine them into a single, sequential action to avoid data corruption.
Also, steer clear if the flow is extremely short and simple. For two simple actions that take milliseconds to complete, the overhead of creating and managing the parallel branches might actually make the flow marginally slower or, at the very least, unnecessarily complex. Don't optimize for the sake of optimizing; optimize for a measurable performance gain.
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