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Two things dominate how fast you get audio and how good it sounds: the nfe setting and cold starts.

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nfe — the quality/speed dial

nfe (number of function evaluations) is how many diffusion steps the model runs. More steps = better quality, more time.
Rule of thumb: start at 32; drop to 16 when responsiveness matters more than the last bit of fidelity.

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Cold starts

The GPU backend scales to zero when idle to save cost. Consequences:
  • The first request after an idle period pays a cold start — this can be tens of seconds.
  • After a request, the service stays warm for a few minutes, so follow-up calls are fast.
  • The SDK’s default 120 s timeout is sized for this. Don’t lower it below what a cold start needs unless you know the service is warm.
Keeping it warm: if you have predictable traffic, a lightweight periodic geko.health() (or a pre-warm call before a known burst) keeps a container hot. Always-on warmth is a server-side deployment choice.

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Other factors

  • Text length. Longer text = longer synthesis (roughly linear). Break very long inputs into sentences/paragraphs and synthesize in parallel if you need throughput.
  • speed. Changes playback pace (0.5–2), not generation time.
  • Concurrency. Independent requests run concurrently; the SDK doesn’t serialize them.

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Measuring

Time a warm call end-to-end:
Run it twice — the second number (warm) is the one your users will usually see.

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Next steps

Streaming

Start playback sooner by synthesizing sentence-by-sentence.

Voice agents

Wire low-latency TTS into a real-time voice loop.

Limits & constraints

Text limits, output format, and cold starts.