🌟 Full-Stack Mobile Engineer (iOS & Android)

About Spirit

Spirit is an angel-backed, ambitious startup building an emotional, ethically-designed AI companion product that blends beautiful 3D/AR experiences, voice, and contextual memory — all powered by AI. Our goal is to create companions that feel alive, personal, and emotionally intelligent — not just chatbots, but presence.

We’re a lean, hands-on team where every engineer owns major pieces of the experience. You’ll work directly with founders and AI engineers to define how people emotionally connect with digital beings — from interface to infrastructure.

About the Role

We’re looking for a Full-Stack Mobile (and Web!) Engineer who can take Spirit from prototype to production. You’ll architect and build our cross-platform mobile app (iOS & Android), integrating real-time 3D avatars, LLM-driven interactions, and cloud-backed personalization.

You’ll own both the frontend (React Native + AR) and backend (Node.js, Python, AWS) layers, ensuring seamless communication between the mobile client, our AI services, and memory databases.

This role is perfect for someone who loves both creative engineering and product thinking — designing interfaces that feel magical while ensuring the systems behind them are fast, secure, and scalable.

Responsibilities

• Design and build Spirit’s cross-platform mobile app (React Native + Expo or Flutter).

• Design and build Spirit’s 3D web app (NextJS, Typescript, Tailwind).

• Implement immersive 3D and AR experiences using React Native ARKit, Three.js, or Unity as a Library for avatar rendering and animation.

• Develop APIs and backend services (Node.js + Express / NestJS or Python + FastAPI) that handle chat sessions, user memory, and personalization.

• Integrate LLMs and AI APIs (OpenAI, Anthropic, or local inference models) for conversational and emotional intelligence.

• Build real-time pipelines for chat, voice, and avatar interaction using WebSockets / Socket.IO.

• Design and manage databases for context persistence (PostgreSQL + Redis or MongoDB + vector search like Pinecone / FAISS).

• Deploy and scale backend systems using AWS (ECS / Lambda / API Gateway / DynamoDB) or GCP Cloud Run + Firestore.

• Collaborate with designers to ensure fluid, emotionally resonant UI/UX — including transitions, animations, and interactions.

• Maintain best practices in testing, version control (Git), CI/CD (GitHub Actions), and code documentation.

• Drive architectural decisions for mobile performance, offline caching, and data privacy.

Tech Stack

Frontend

• React Native (TypeScript), Flutter for iOS/Android and NextJS, TailwindCSS for Web App

• Expo / React Navigation / Redux Toolkit for structure

• Three.js, Babylon.js, or Unity (as plugin) for 3D/AR

• Lottie / Reanimated / Framer Motion for animation

• WebRTC / WebSocket / Voice APIs for real-time communication

Backend

• Node.js + Express/NestJS or Python + FastAPI

• GraphQL / REST API integration

• OpenAI, Gemini APIs for LLM integration

• WebSocket / Socket.IO for low-latency messaging

• Authentication via Clerk, Firebase Auth or Cognito

Database / Storage

• PostgreSQL / Supabase for structured data

• Redis / Pinecone / FAISS for embeddings and short-term memory

• S3 / Cloud Storage for media, voice, and avatar assets

Cloud & DevOps

• AWS (ECS Fargate, Lambda, API Gateway, S3, RDS) or GCP (Cloud Run, Firestore)

• Docker for containerization

• Kubernetes for container orchestration

• GitHub Actions / CircleCI for CI/CD

• Monitoring with Datadog or OpenTelemetry

Requirements

• Proven experience building mobile and web apps (React Native or Flutter) from scratch.

• Solid backend development experience (Node.js or Python) and ability to design RESTful or GraphQL APIs.

• Strong grasp of frontend architecture, component design, and state management.

• Knowledge of databases (SQL and NoSQL) and cloud deployment pipelines.

• Familiarity with AI/LLM API integration (e.g., OpenAI, Hugging Face).

• Excellent sense of UI/UX design, especially in animation, microinteractions, and user emotion.

• Passion for real-time systems, 3D interfaces, and AR experiences.

Nice to Have

• Prior experience with ARKit / ARCore / Unity3D.

• Experience optimizing 3D rendering or motion design on mobile.

• Exposure to LLM memory systems or vector databases.

• Familiarity with privacy-first data design and local caching.

• A personal app, open-source contribution, or creative tech project that showcases your imagination.

Why Join Spirit?

• Work directly with founders on a product that merges AI, art, and emotion.

• You’ll ship live to users — not into a backlog.

• Learn cutting-edge tools in LLMs, AR, and 3D while shaping an early product from zero to launch.

• Contribute ideas to product, design, and AI direction — you’re not just an engineer, you’re a co-creator.

• Flexible remote setup, creative autonomy, and fast growth potential.

• Exceptional contributors will be considered for early equity and leadership roles.

• Be part of a collaborative, mission-driven team that values innovation, experimentation, and creative problem-solving.