Which Azure Stream Analytics metric shows the count of input events that were not processed by the job?

Backlogged Input Events is the correct metric because it directly indicates the number of input events that have arrived but have not yet been processed by the Stream Analytics job. A high number here suggests a processing bottleneck or insufficient resources. Out-of-Order Events refers to events arriving outside their expected timestamp order, which Stream Analytics can handle, but doesn't mean they are unprocessed. Output Events counts the events successfully produced by the job, not those waiting to be processed. Late Input Events are those that arrive after their defined maximum arrival delay, which also doesn't directly represent unprocessed events currently in the queue.