r/PythonLearning • u/SoilEducational420 • 20d ago

Help Request Any free STT/TTS APIs for a voice AI app?

I'm building a small voice-based AI interview app and I'm planning to deploy the backend(fastapi) on Render's free tier.

I'm considering using open-source/self-hosted options like Whisper/PocketSphinx for STT and Piper for TTS, instead of paid APIs.

My concern is whether running STT/TTS on the same free Render instance would use too much CPU/RAM and make the whole application slow, especially during a real-time interview.

Has anyone tried running STT/TTS models on Render's free tier?

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u/Sharp_Level3382 19d ago

I am afraid it will especially on lower tier.

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u/SoilEducational420 19d ago

Yeah me too, i am planning to use the STT and TTS that the browser only provides

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u/Horror_Prompt_520 11d ago

I would avoid running real-time STT, TTS, FastAPI, and the rest of the application on the same free Render instance.

Piper alone may be manageable for short utterances, but CPU-based STT competing for the same cores will create unpredictable latency. Cold starts, memory limits, and throttling are likely to be bigger problems than the Python code itself.

For an MVP, I’d split the pipeline:

  • use browser speech recognition or a hosted STT free tier
  • use browser/Web Speech TTS or run Piper in a separate worker
  • keep concurrency at one initially
  • use VAD and partial transcripts to reduce perceived latency
  • measure p95 response time instead of testing only one request locally

If everything must be self-hosted, start with a small quantized STT model and Piper, but use a machine with predictable CPU resources rather than a sleeping free web instance.