Slow Time to First Byte (TTFB)

What this check looks for

Checks how long the server takes to send the first byte of the response after the browser requests the page.

Why it matters

TTFB captures server processing, database queries, and network latency before any rendering can start, so a slow first byte delays every downstream metric including Largest Contentful Paint. Google's guidance treats a TTFB under about 800ms as a reasonable target for a good experience. Caching, a CDN, faster backend queries, and edge rendering are the usual levers to bring it down.

How to fix it

# Cache full HTML responses at the edge/proxy to slash TTFB on repeat hits
proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=html_cache:10m max_size=500m inactive=60m;

location / {
    proxy_cache html_cache;
    proxy_cache_valid 200 10m;
    add_header X-Cache-Status $upstream_cache_status;
    proxy_pass http://app_upstream;
}

Go deeper

• Website speed optimization guide →