Redirect only few Kafka messages to new application to check flow is good

I am aware of consumer group concept in kafka.We have Application A which currently takes a lot of traffic. We built a new Application B which also listens to same kafka topic. We initially want new Application B to take a very small percentage of traffic like if Application A process 1000 messages then I want Application B to get 1 message and process it. That way I can check if new Application processing is good before redirecting all traffic to new Application B. Both applications will have diff consumer group and different db. How do we design so that new Application B gets only a small percentage of population and avoid duplicate processing between application A and Application B

How to have a mechanism in Kafka to redirect only small percentage to new appliation