Optimizing TTFT Across 6 LLM Providers in Next.js

Time to First Token (TTFT) is the single most important latency metric for streaming AI interfaces. It measures the delay between sending a prompt and receiving the first chunk of the response. For a browser-only workbench like AIWorkbench.dev, every millisecond counts.

What is TTFT and Why It Matters

TTFT directly impacts perceived responsiveness. Users tolerate a loading spinner for a few seconds, but once they see a streaming cursor, they expect it to move immediately. A TTFT over 1.5 seconds feels broken. Under 500ms feels native.

Provider	Median TTFT	Streaming
Anthropic Claude	800-1200ms	Server-Sent Events
OpenAI GPT-4o	600-900ms	Server-Sent Events
Google Gemini	700-1000ms	Server-Sent Events
AWS Bedrock	1200-2000ms	Server-Sent Events
DeepSeek	1500-3000ms	Server-Sent Events
Meta Llama	1000-1500ms	Server-Sent Events

The Browser-Only Architecture Advantage

Most AI wrappers route requests through their own backend. This adds a network hop: your browser → their server → provider API → their server → your browser. That's two extra legs.

AIWorkbench.dev eliminates the middleman. The browser makes a direct HTTPS request to the provider's endpoint. This alone saves 100-300ms of proxy latency.

Next.js Optimizations for Streaming

1. Use Native fetch with ReadableStream

Do not buffer the entire response in memory. Pipe the provider's Server-Sent Events directly into a ReadableStream consumer:

const response = await fetch('https://api.anthropic.com/v1/messages', {
  method: 'POST',
  headers: { 'anthropic-version': '2023-06-01' },
  body: JSON.stringify({ stream: true, ...payload }),
});

const reader = response.body!.getReader();
while (true) {
  const { done, value } = await reader.read();
  if (done) break;
  // Decode and parse SSE chunks here
}

2. AbortController for Instant Cancellation

Always attach an AbortController. If the user clicks "Stop" or navigates away, immediately terminate the fetch:

const controller = new AbortController();
fetch(url, { signal: controller.signal });
// On cleanup: controller.abort();

3. Debounce UI Updates

Parsing SSE chunks can trigger 50+ React re-renders per second. Accumulate tokens in a ref and batch state updates every 100ms to prevent frame drops.

Key Takeaway

TTFT is a network problem, not a model problem. Remove proxies, stream directly, and batch UI updates. Your users will thank you.