Hi @Satya Reddi , 

1. If a Stream node is not available, it will significantly impact the functioning of Queue Processors in Pega because Queue Processors rely on Kafka-based stream services, which are managed by Stream nodes. 
2. Without an active Stream node, the Queue Processor cannot access the Kafka topics that are used to store and manage queued items. As a result, it will stop processing messages.
3. Any messages that are in the queue will remain there until a Stream node becomes available. The Queue Processor will not lose these messages; they will remain in Kafka, waiting to be processed when the Stream node is restored.

Once the Stream node becomes available, the Queue Processor will automatically resume processing the messages in the queue, and any new messages can be enqueued and processed normally

Regards,

Mohd Qizer Uddin

@Satya Reddi

f the stream node is not available the system stores the message in the database. A job scheduler runs periodically to check whether the stream node is running. If the stream node is found to be running, the job scheduler queues all such delayed messages to the Kafka Topic.