The way NGINX handles the TCP connection for load balancing and connection reuse may be the cause of the behavior you are observing, where there are active connections between the NGINX Ingress controller and destination pod even in the absence of client requests.

It should be noted that NGINX contains a keepalive directive that specifies how many connections should be maintained open in the connection pool. As a result, you may see some connections are left open even when no client requests are coming in. Refer to this for more information on this.

Also you can configure the NGINX ingress controller to have a shorter keep-alive timeout to close idle connections faster. In simple words **you can modify the NGINX configurations by setting a lower keep_alive timeout for TCP connections.**For more information on this keepalive connections refer to this blog by Timo Stark.