Senior Full Stack Engineer (AI + Flutter)

About TWINii

A life's work.

An expert spends decades building knowledge that only a handful of people ever get direct access to. TWINii turns that life's work into personal conversations at scale, so the people who need their thinking can actually talk it through with them.

We are live on the App Store and Google Play, funded, with real users on a paid subscription tier talking to expert TWINiis by voice and chat. Engineering is around ten people, mostly across India, on a daily standup.

The Role

This is a hands-on individual contributor role. No direct reports, no team to manage. You write code every day.

You will own features across our backend services, AI orchestration layer and web interfaces, end to end, from design through to production. That is the majority of the job.

The rest is Flutter. Our product is mobile-first and we need full stack engineers who do not stop at the API boundary. When a feature needs the app, you build it in the app. You will not be the mobile lead and you will not be alone in there, but you will be expected to open the Flutter codebase, ship a well-built feature, and debug a problem that starts in the app and ends in an AI pipeline.

If your experience is limited to one layer of the stack, or you treat mobile as somebody else's problem, this is not the right role.

What you'll do

• Build backend services and APIs in Node.js and Python, at production scale
• Build and operate AI workflows using LangChain and LangGraph for orchestration, chaining and agent logic
• Trace, evaluate and debug AI pipelines in production with LangSmith
• Integrate real-time voice using LiveKit
• Build web interfaces in React and Next.js that handle streaming AI responses cleanly
• Ship features in our Flutter app for iOS and Android
• Debug problems that span the app, the backend, the AI pipeline and the infrastructure at once

What you need

• 5+ years professional software engineering in production environments
• Strong Node.js and Python at production scale
• Shipped AI workflows using LangChain, LangGraph or comparable frameworks
• Production Flutter and Dart. You have shipped a Flutter app to the App Store or Play Store, or contributed substantial features to one, and you are comfortable working in someone else's Flutter codebase
• React and Next.js or equivalent
• MongoDB or similar document stores
• AWS, GCP or equivalent cloud environments
• Strong async programming and streaming (SSE / WebSocket) on both web and mobile

Nice to have

• LiveKit or other real-time voice and audio pipeline systems
• Conversational AI, voice agents or multi-modal AI products
• Swift or Kotlin native depth
• Mobile CI/CD with Fastlane or GitHub Actions
• RAG pipelines or LLM evaluation
• RevenueCat, Stripe or in-app purchase flows

What senior means here

Senior here means depth and ownership, not headcount. You do not need a task list to know what to work on. If something breaks in production you are already investigating before anyone asks. You have opinions on architecture you can defend with reasoning. You have shipped and maintained a product over time, not just built features and moved on. You leave code and documentation in better shape than you found it.

What you get

End-to-end ownership of features that ship to real, paying users. Direct influence over technical and architectural decisions. A live product with real usage data rather than a roadmap of hypotheticals. A small, senior team where your work is visible in the product.

No AI-scripted CVs or answers.