Devang S.

Full Stack AI Engineer | Voice AI, AI Agents, Node.js & Next.js

Full-Stack AI Engineer who ships production AI voice agents, AI agents, and scalable web apps end to end. I built Fonazo, a live AI voice agent that answers business calls and books appointments, and scaled Satlantis solo from zero to 300,000+ users. Today I build AI-powered CRM agents at Chirp on Mastra and LangGraph. 100% Job Success on Upwork across 15+ delivered projects, every one 5 stars. I own the whole thing: the voice pipeline, the agent, the API, the database, and the polished frontend on top. WHAT I BUILD • AI voice agents on a real-time Python pipeline (Pipecat, VAD, streaming speech-to-text and text-to-speech, and any LLM: OpenAI, Anthropic, Groq). I built Fonazo, a production AI voice agent that answers calls, books appointments, qualifies leads, and updates the CRM live in 40+ languages, plus Call Assist, an AI receptionist with sub-second turn-taking over Twilio and Deepgram. • AI agents and workflow automation with Mastra, LangGraph, the Vercel AI SDK, function calling, and RAG on PostgreSQL and Redis. At Chirp this cut manual workflow execution time by 60% across customer accounts. • SvelteKit and Next.js web apps built to ship and hold up in production. I scaled Satlantis to 300k+ users at 99.9% uptime and cut load time 30% with SSR and Go caching layers. • Real-time systems: WebRTC and WebSocket audio/video, live chat, and presence. I built a full Discord clone with LiveKit calls and sub-200ms messaging. • Go backends and developer tools: REST and tRPC APIs, queue-based job runners, OAuth2 auth servers, plus a language interpreter and a Git-like version control system written from scratch in Go. STACK Voice AI: Python, Pipecat, VAD, streaming STT and TTS (Deepgram, ElevenLabs, Cartesia), Twilio and telephony, any LLM AI and agents: Mastra, LangGraph, LangChain, Vercel AI SDK, RAG, pgvector, function calling, OpenAI, Anthropic, Groq Frontend: SvelteKit, Svelte, Next.js, React, TypeScript, Tailwind CSS, Astro, shadcn/ui Backend: Node.js, NestJS, Go (Chi), FastAPI, tRPC, GraphQL, REST, gRPC Real-time and media: WebSockets, WebRTC, SocketIO, LiveKit, Twilio Data: PostgreSQL, MySQL, MongoDB, Redis, Supabase, Firebase Infra: Docker, AWS, GitHub Actions, CI/CD, Cloudflare, Nginx WHERE I FIT BEST • You want an AI agent or voice agent built for real users, not a demo • You have a SvelteKit or Next.js app that needs to ship or scale • You need real-time features (calls, live chat, collaboration) done properly • You want one engineer who takes an idea to production across the whole stack Tell me what you are building and the outcome you need. I reply within hours and I will tell you straight whether I am the right fit.