Time to First Byte (TTFB)What it checks and how to fix it

What it checks

Times a request to the page and reports the time to first byte, split into DNS lookup, TCP connection, TLS handshake and server processing. Up to 200 ms passes, 201 to 1000 ms warns, and over 1000 ms fails.

Why it matters

Nothing appears on screen until the first byte of HTML arrives, so a slow TTFB delays every other metric, including First Contentful Paint and LCP. It usually points at slow server-side rendering, uncached database queries or a server far from the visitor.

How to fix it

Use the breakdown to see where the time goes. Slow DNS or TLS: use a faster DNS provider and a CDN. Slow server processing: profile the request and cache what you can.

Cloudflare: cache HTML at the edge for anonymous pages with a Cache Rule ("Eligible for cache") so most requests never reach the origin.

nginx micro-caching in front of an app server

proxy_cache_path /var/cache/nginx keys_zone=pages:10m max_size=1g;
location / {
  proxy_cache pages;
  proxy_cache_valid 200 1m;
  proxy_pass http://app;
}

Rails: find slow queries (N+1s, missing indexes) in the logs or an APM, and cache rendered fragments and HTTP responses.

def show
  @page = Page.find(params[:id])
  fresh_when @page, public: true
end