How to not allow forward traffic to backend side during INIT state

Is it possible or not? I’m looking for a solution when incoming traffic isn’t allowed to get in backend side during HAPROXY is in INIT state.
Allow to forward traffic only if health-check returns OK!

yes, this is possible. Just set up the right health check and ensure the app answers positively once it knows itself it is fully ready.

Thanks for reply. Could I ask you what you mean “right health check”?
For example, I have such configure of my farm

listen FARM_1:5400
    description FARM_1
    bind ip-address:5400
    mode tcp
    timeout connect 5s
    timeout client 60s
    timeout server 60s
    option tcp-check
    rate-limit sessions 30
    tcp-check   send-binary <some-special-bin-string>
    tcp-check expect binary <<some-special-bin-string>
    balance leastconn
    default-server check resolve-opts allow-dup-ip inter 30s fall 1 rise 1 maxconn 1000 
    server SRV1 SRV1:11900 maxconn 1000 weight 100 send-proxy
    server SRV2 SRV2:11900 maxconn 1000 weight 100 send-proxy
    server SRV3 SRV3:11900 maxconn 1000 weight 100 send-proxy

This example includes “tcp health check”. But issue is that haproxy manages to forward connects to backend side be into INIT status. That happens at start-up moment when health check is calculate real status of servers. In my config the tcp-ports on servers’ side are open (L4) and the service which is listen to it administratively restricts connects. HAPROXY sends health check (L7) and receives answer (L7). If the answer - true, the server is ready to serve clients, else - not. In my case server configured to send negative health check to HAPROXY that means the servers do not have to have clients.

You might want to take a look here
It’s the help for the statement
tcp-check connect

Also check the statements around it, like tcp-check expect etc

Hope it helps