The RESTBase API doc at http://restbase.wikimedia.org/fr.wikipedia.org/v1/?doc mentions:

As a general rule, don't perform more than 200 requests/s to

@BBlack recently introduced a rate limiter in Varnish which limits requests to 50/secs:

modules/varnish/templates/vcl/wikimedia.vcl.erb:

sub misspass_limiter {
    if (ipcast.ip(req.http.X-Client-IP, "127.0.0.1") !~ wikimedia_nets) {
        // TBF: "1, 0.02s, 250" == "50/s, burst of 250"
        if (!tbf.rate(req.http.X-Client-IP, 1, 0.02s, 250)) {
            error 429 "Request Rate Exceeded";
        }
    }
}

Maybe we should only mention the actual rate limit on the already linked page https://www.mediawiki.org/wiki/API_versioning then add a comment in VCL to remember folks to update the wikipage.