@F_Amini  @Green_ Is absolutely correct here.  You should be careful when increasing concurrent tasks as just blindly increasing it everywhere can have the opposite effect on throughput.  I recommend stopping setting the concurrent tasks back to 1 or maybe 2 on all the processor where you have adjusted away from the default of 1 concurrent task. Then take a look at the processor further downstream in your dataflow where it has a red input connection but black (no backpressure) outbound connections.  This processor s @Green_ mentioned is the processor causing all your upstream backlog.  Your'll want to monitor your CPU usage as you make small incremental adjustments to this processors concurrent tasks until you see the upstream backlog start to come down.   If while monitoring CPU, you see it spike pretty consistently at 100% usage across all your cores, then your dataflow has pretty much reached the max throughput it can handle for yoru specific dataflow design.  At this point you need to look at other options like setting up a NiFi cluster where this work load can be spread across multiple servers or designing your datafow differently with different processors to accomplish same use case that may have a lesser impact on CPU (not always a possibility).  Thanks, Matt ... View more