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Get Started Free →Use when auditing slow first responses on SSR pages, APIs, or cacheable HTML. Distinguish origin compute time from network latency and CDN cache misses before proposing a fix.
| Test case | Without → With | Effect | Δ tokens | Δ turns |
|---|---|---|---|---|
| case-01 | ✗→✓ | ▲ Improved | 153% | 0% |
| case-02 | ✗→✓ | ▲ Improved | 21% | 0% |
| case-10 | ✗→✓ | ▲ Improved | 8% | 0% |
| case-11 | ✗→✓ | ▲ Improved | 16% | 0% |
| case-20 | ✗→✓ | ▲ Improved | -22% | 0% |
TTFB is the foundation of page performance; if the server is slow to respond, all subsequent loading stages are delayed.
Review the page's TTFB and identify any bottlenecks in the server-side processing or network transmission.
Optimize the server's response time by improving database queries, caching responses, and using a CDN.
Explain how TTFB impacts the entire page load process and why it is a critical starting point for performance optimization.
Review server-rendered routes, API handlers, cache configuration, and database access on the critical path. Flag uncached HTML, slow synchronous work before the first byte, repeated upstream fetches, or expensive queries that keep TTFB above roughly 800ms.
For full implementation details, code examples, and framework-specific guidance, see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/performance/ttfb
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