ConnectWebSocket processor sending around only 1 message per second

I was using ConnectWebSocket Processor to Listen to data from Websocket. Everything was working fine until we did some stress tests. We have sent 320 messages to WebSocket at the same moment. In Nifi it takes around 5 min to pull them all, however, at the same time I have created a simple Java application that listens to everything in almost real-time. 

Looks like the processor sends 60 messages per minute, I am using Nifi-2-0-0-M2 in 3 node cluster.

According to slack conversation, it can be legacy code but hard to assess 
https://apachenifi.slack.com/archives/C0L9S92JY/p1710770819875619