Leaky bucket method with Haproxy - Rate limiting

Nginx uses the leaky bucket method to limit request rate. Nginx http_limit_req_module.

It means that if I set a limit to 100 req/sec, and then I get flooded by 120 req/sec, 100 requests will be served normally but 20 requests will be served by a 503 error.

How can I setup this with Haproxy?

I read a lot of the documentation about sc_http_req_rate but since the rate is always 120 req/sec. I am always returning 503 errors.

frontend main
    bind *:80
    acl foo_limited_req sc_http_req_rate(0) ge 100
    http-request track-sc0 path table Abuse     # Set the URI as the key of the table
    use_backend bk1 if foo_limited_req
    default_backend web

backend web
    server web1

backend Abuse
    stick-table type string len 128 size 100K expire 30m store http_req_rate(1s)

backend bk1
     server listenerror

listen errorlistener
    mode http
    errorfile 503 /etc/haproxy/errors/200-tuned.http

I want to serve the flow of 100 req/sec with web backend. And the 20 req/sec surplus with bk1 backend. I am using Haproxy version 1.9.2.

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