ForEach and Parallel ForEach

⚡For Each Scope

Configuration:

• Collection: Expression that defines the collection.
• Counter Variable Name: Stores the iteration count.
• Batch Size: Splits the collection into sub-collections based on the specified value.
• Root Message Variable Name: Stores the original payload.

Behavior:

• Splits the payload into elements and processes them sequentially.
• Executes in order (one by one).
• Does not modify the payload — outside the scope, the payload remains the same as the initial input.
• Variables declared inside the scope are accessible outside.
• If one element fails, an exception is thrown, and For Each stops processing unless error handling is implemented.

⚡ Parallel For Each Scope

Configuration:

• Collection: Expression that defines the collection.
• Timeout: Maximum execution time (in ms). If exceeded, a timeout error is raised.
• Max Concurrency: Defines the number of parallel threads to run at once.
• Target Value: Stores the processed payload (defaults to flow’s payload).
• Target Variable: Stores the evaluated expression result (defaults to the operation output).

Behavior:

• Splits the collection and processes elements in parallel.
• Onces it finishes the execution it aggregates the output and gives the final payload.
• Execution order is not guaranteed.
• Variables declared outside the scope remain unchanged even if modified inside.
• Variables declared inside are not accessible outside.
• Variables are independent to each event inside paralle foreach.
• If an error occurs, a composite error is thrown, and the scope terminates.
• Failed records can be handled using error handling (e.g., Try + On Error Continue).

📝 Key Takeaways

• Use For Each when you need sequential processing and payload consistency.
• Use Parallel For Each for faster processing of large datasets where order doesn’t matter.
• Always implement proper error handling (Try + On Error Continue) to avoid failures stopping the flow.

📝 Interview Questions

• You have 10,000 records. Which scope will you use and why?
• If 1 record fails in Parallel For Each, what happens?
• How does For Each differ from a Batch Job?
• What is the role of the Counter Variable Name in For Each?
• Are variables declared inside For Each accessible outside the scope?
• Does For Each modify the payload inside the scope? What happens outside?
• How are results aggregated after parallel execution?
• Are variables declared inside Parallel For Each accessible outside? Why not?
• How does error handling behave in Parallel For Each? What is a composite error?