Deepgram Interview Practice App

Simple local app for real-time interview practice using Deepgram's Voice Agent API with an Express backend and server-side websocket proxy.

What it does

• Streams your microphone to Deepgram in real time
• Uses Deepgram's Voice Agent API for STT + managed LLM + TTS in one websocket
• Proxies the realtime websocket through the backend so the browser never sees the Deepgram API key
• Plays the agent's audio reply immediately
• Stops playback when you interrupt and start speaking again

Setup

1. Either create a .env file in the project root:

DEEPGRAM_API_KEY=your_key_here
PORT=3000
ALLOWED_ORIGINS=http://127.0.0.1:3000,http://localhost:3000

Or set your Deepgram API key in the shell before starting the server:

$env:DEEPGRAM_API_KEY="your_key_here"

2. Start the app:

node .\server.js

3. Open http://127.0.0.1:3000

Notes

• The server keeps your Deepgram API key entirely on the backend and opens the Deepgram Voice Agent websocket server-side with Authorization: Token <API_KEY>.
• Because the browser talks only to your local Express websocket proxy, this app does not depend on Deepgram browser token minting and does not require a Member key just to generate frontend JWTs.
• The Voice Agent settings in this app explicitly set agent.think.provider to a managed model so the payload matches Deepgram's current schema.
• The local /ws proxy accepts only approved origins by default. Override ALLOWED_ORIGINS only if you intentionally host the UI elsewhere.
• If you add or change the key, restart node .\server.js so the server picks it up.
• This app uses Deepgram's Voice Agent API because it bundles speech-to-text, LLM orchestration, text-to-speech, and interruption-aware conversation flow.
• If your browser blocks autoplay, click the page once and then start the session again.

Backend

• server.js is the entry point.
• src/config.js loads environment variables and backend config.
• src/server.js runs the Express app, static hosting, health/config routes, and the websocket proxy to Deepgram.