Selective hydration lets the shell paint immediately while slower subtrees stream in1, and time-to-first-token in production is dominated by queueing and prefill rather than raw generation speed2.
Sources
1Streaming SSR with React Server Components react.devSelective hydration lets the shell paint immediately while slower subtrees stream in as they resolve.
2Measuring Time to First Token in production vercel.comTTFT is dominated by queueing and prefill; chunked transfer keeps perceived latency flat.