HAProxy Load Distribution and Backend Application Autoscaling

Help!
1

Scenario: I’m running an HAProxy instance in two clusters, and my backend application is deployed across five different clusters. Despite generating significant load, my backend application does not seem to be scaling up as expected. I suspect that HAProxy might not be forwarding the load effectively and requests are getting queued. I’ve already set timeout queue to 5s to minimize queuing.

global
    maxconn 5000
    log stdout format iso local0

defaults
    log global
    mode http
    option httplog
    option http-keep-alive
    option redispatch
    option log-health-checks
    option forwardfor
    timeout http-request 10s
    timeout queue 5s
    timeout connect 5s
    timeout client 30s
    timeout server 30s
    timeout http-keep-alive 10s
    retries 3

listen fe_haproxy_stats
    bind *:8500
    mode http
    stats enable
    stats realm "Haproxy\\ Statistics"
    stats uri /stats
    stats refresh 30s
    http-request set-log-level silent

frontend fe_main_https_in
    bind *:8080
    acl is_api path /test
    use_backend bk_2 if is_api
    default_backend bk

backend bk
    mode http
    balance roundrobin
    option httpchk GET /health
    http-check expect status 200
    http-send-name-header Host
    http-response set-log-level silent if { status 200 }
    default-server inter 2s fall 3 rise 2 ssl verify required ca-file /usr/local/etc/haproxy/cert/root.pem
    server url1.com url1.com:443 check check-sni "url1.com" sni str("url1.com")
    server url2.com url2.com:443 check check-sni "url2.com" sni str("url2.com")
    server url3.com url3.com:443 check check-sni "url3.com" sni str("url3.com")
    server url4.com url4.com:443 check check-sni "url4.com" sni str("url4.com")
    server url5.com url5.com:443 check check-sni "url5.com" sni str("url5.com")

backend bk_2
    mode http
    balance roundrobin
    option httpchk GET /health
    http-check expect status 200
    http-send-name-header Host
    http-response set-log-level silent if { status 200 }
    default-server inter 2s fall 3 rise 2 ssl verify required ca-file /usr/local/etc/haproxy/cert/root.pem
    server url4.com url4.com:443 check check-sni "url4.com" sni str("url4.com")
    server url5.com url5.com:443 check check-sni "url5.com" sni str("url5.com")

Are there any other configurations I should consider to ensure HAProxy forwards the load effectively, allowing the backend application to scale up as needed? Also, is it worth deploying HAProxy in 5 clusters the same as backend? (Using HAProxy 3.0.2)

Thank you for your assistance!