Senior Full-Stack Engineer (5+ yrs) - React Native + Node.js AI voice companion App, Phase 2,

About the product Marujigi is a Korean AI voice companion for seniors aged 70+, paired with a Family app for their adult children and caregivers. Phase 1 (MVP) is in testing: tap-to-talk voice conversation (Naver CLOVA STT/TTS + LLM), SMS-based scam detection, wellness check-ins, and family notifications. Stack: React Native (iOS + Android), Node.js/TypeScript backend, PostgreSQL (Supabase), Firebase FCM, Naver Cloud (Object Storage, CDN, SENS SMS/KakaoTalk), OpenAI API via an LLM adapter layer, Apple/Google in-app subscriptions. Your role: engineer + tech lead The MVP was built by an external contractor. In Phase 2 you will: - Audit the existing codebase, infrastructure and documentation, and deliver a handover/risk assessment within the first 2 weeks - Coordinate the current contractor during the transition (scope, code review, acceptance of deliverables) while taking ownership of the repo, CI and environments - Set up engineering foundations we can hire into: repo structure, coding standards, review process, deployment pipeline, runbooks - Lead the move to in-house development — you'll be our first engineer and will help interview and onboard the next ones as we grow Roadmap — this is a long-term engagement Phase 2 (this contract, 6–24 months) - Feature additions to the existing apps: multiple parents/family members in the Family app, additional family links in the Senior app, voice conversation in the Family app, subscription tiers with per-tier daily turn limits, 7-day free trial, early-bird pricing - B2G / B2B platform (main focus): organization accounts for municipalities and nursing/care facilities — multi-tenant data model, caregiver/admin roles, bulk onboarding of seniors without email, dashboards and periodic reports, per-org configuration, and a web admin console - Locale abstraction: parameterize the Korean implementation so persona prompts, STT/TTS config and content strings load as locale packs (English first) - Hardening: logging, error tracking, test coverage, CI for store builds Phase 2.5 (ongoing after core delivery) - Cognitive games and cognitive-assessment test modules inside the Senior app (platform-policy-safe), capturing measurable signals such as reaction time and response latency alongside voice-based indicators Phase 3 - Integration with a wearable device (LTE smartwatch): location/SOS, step count and heart-rate wellness data, voice conversation from the watch, HealthKit / Health Connect background delivery Who we're looking for - 5+ years full-stack experience with at least 5 shipped React Native apps on both stores - Strong Node.js/TypeScript and PostgreSQL; comfortable owning backend, mobile and a web admin console end to end - You've taken over someone else's production codebase before and can describe how you de-risked it - You've led or coordinated other developers (contractors or a small team) — code review, task breakdown, acceptance criteria - Hands-on experience designing multi-tenant / role-based B2B systems (org → admin → caregiver → end user) - Experience with LLM API integration (OpenAI/Anthropic/Gemini), streaming responses, prompt/config management - Experience with in-app purchases (StoreKit 2 / Google Play Billing) and push notifications - Clear written English; proactive, asynchronous communicator - Bonus: Supabase, Naver Cloud, Korean language, healthcare/eldercare products, BLE or wearable integration How we work - Remote, async-first. Daily written update + 2 short calls/week (KST afternoon / IST morning overlap) - Code in GitHub, tasks on a shared board, decisions documented in writing - Credentials issued via least-privilege sub-accounts and one-time secret links — never pasted in chat - Start with a paid 2-week trial milestone (codebase audit + handover report + one small feature). If it works out, this becomes an ongoing contract covering Phase 2.5 and Phase 3, with a path to a full-time in-house lead role after funding To apply Start your proposal with the word "MARU" and include: 1. Links to 2 React Native apps you shipped (App Store / Play Store) 2. One example where you inherited an existing codebase from another developer or vendor — what did you find, and what did you fix first? 3. One example of a multi-tenant or role-based B2B system you built — how did you model orgs and permissions? 4. One example of an LLM or voice feature you built — what was hard about it? 5. Your availability (hours/week) and earliest start date Generic or AI-written proposals without the above will be skipped.