Magento 2 Varnish cache not working – 0% hit rate and wrong VCL config

Varnish was installed and configured, but every request was hitting PHP – hit rate was 0%. The server was overloaded despite Varnish. The problem was in wrong VCL configuration and session cookies. Fix time: 4 hours.

Symptoms

• Varnish running (port 6081), nginx listening on 8080
• varnishstat shows MAIN.cache_hit = 0
• Response header: X-Cache: MISS on every request
• PHP server overloaded despite Varnish

Cause

Magento was sending a PHPSESSID cookie on pages that should be cached. Varnish by default does not cache requests with cookies. The VCL also lacked a rule to strip PHP session cookies on static pages.

Solution

# Generate correct VCL from Magento
bin/magento varnish:vcl:generate     --export-version=6     --output-file=/etc/varnish/default.vcl

# Reload Varnish with new VCL
varnishadm vcl.load m2 /etc/varnish/default.vcl
varnishadm vcl.use m2

sub vcl_recv {
    # Remove cookies for static assets
    if (req.url ~ "\.(jpg|jpeg|png|gif|css|js|ico|woff)$") {
        unset req.http.Cookie;
        return (hash);
    }

    # Strip non-essential cookies
    if (req.http.Cookie) {
        set req.http.Cookie = regsuball(req.http.Cookie,
            "PHPSESSID=[^;]+;?\s*", "");
        if (req.http.Cookie == "") {
            unset req.http.Cookie;
        }
    }
}

Result

Hit rate after fix: 94%. PHP-FPM load: dropped from 80% to 8%. TTFB on home page: from 2.1s to 0.04s.