Time to First Byte (TTFB) Budget and Optimization
Set and track Time to First Byte budgets. Understand how TTFB impacts all other performance metrics and strategies for reducing server response time including CDN, caching, and edge computing.
Detailed Explanation
TTFB Performance Budgets
Time to First Byte (TTFB) measures the time from when the browser sends a request to when it receives the first byte of the response. It is the foundation metric — every other timing metric (FCP, LCP, TTI) is delayed by a slow TTFB.
TTFB Thresholds
| Rating | TTFB |
|---|---|
| Good | < 800 ms |
| OK | < 1800 ms |
| Poor | > 1800 ms |
Budget Recommendations
| Architecture | TTFB Target |
|---|---|
| Static site (CDN) | < 100 ms |
| SSG + CDN | < 200 ms |
| SSR + CDN | < 400 ms |
| SSR (no CDN) | < 600 ms |
| Dynamic (API) | < 800 ms |
What Contributes to TTFB
TTFB = DNS lookup + TCP connection + TLS handshake + Server processing + Network latency
Each component adds time:
- DNS lookup: 20-120 ms (cached vs uncached)
- TCP connection: 50-200 ms (depends on distance)
- TLS handshake: 50-150 ms (TLS 1.3 vs 1.2)
- Server processing: 50-500+ ms (database queries, rendering)
- Network latency: varies by geography
Optimization Strategies
- CDN — Serve from edge locations close to users (reduces network latency and TCP/TLS time)
- HTTP/2 or HTTP/3 — Connection reuse reduces overhead for subsequent requests
- Server-side caching — Cache database queries, rendered HTML, API responses
- Edge computing — Run server logic at CDN edge nodes (Cloudflare Workers, Vercel Edge)
- Database optimization — Index queries, connection pooling, read replicas
- Preconnect — Use
<link rel="preconnect">for third-party origins
TTFB and the Budget Tracker
Set your TTFB target in the timing budgets section. While the tracker does not measure actual TTFB (that requires a live server), having the target documented alongside resource budgets ensures the team considers server performance as part of the overall performance budget.
Use Case
TTFB budgets are critical for server-rendered applications and sites with dynamic content. An e-commerce site with a 2-second TTFB cannot possibly achieve a 2.5-second LCP — there is only 500 ms left for resource loading and rendering. Setting a TTFB budget forces the team to invest in server-side performance alongside frontend optimization.