Senior Backend/DevOps (NestJS) - Canada, Mandarin

ABOUT US Novacell Solutions Inc. is a Canadian company building a travel connectivity app: travellers buy a data plan for the country they are visiting and activate it from their phone. Our iOS and Android apps are in store internal-test tracks and we are preparing for public launch. ABOUT THE PROJECT You would be joining an established codebase, not starting a new one: 143 API endpoints, 420 automated tests, and two carrier partners integrated in production. Your first weeks are spent reading code someone else wrote. Stack: NestJS 11, TypeORM, PostgreSQL 17, React 19, React Native (Expo), Docker, GitHub Actions, DigitalOcean App Platform, Prometheus/Grafana/Loki. RESPONSIBILITIES - Design, build and maintain the NestJS and PostgreSQL services behind our order, payment and fulfilment lifecycle, including the carrier partner APIs behind our supplier abstraction layer - Build and extend our operations backend — the admin console, refund handling, and reconciliation between our orders, the payment provider and the carrier partner — both the APIs and the React screens on top of them - Own deployment and operations on DigitalOcean: Docker, CI/CD pipelines, multi-environment configuration, and the release process - Extend monitoring, alerting and structured logging so that production problems are found by us rather than reported by customers - Write and maintain automated tests (Jest, Supertest) alongside the code you ship There is also occasional work on our React Native app's release cycle. REQUIRED QUALIFICATIONS - Based in Canada and able to invoice as an independent contractor - Fluent Mandarin and working English — our product manager, developers and testing team are in China, and some specifications and support content are written in Chinese - 5+ years of professional backend development with strong TypeScript - Deep NestJS experience (modules, dependency injection, guards, interceptors), or equivalent depth in Express or Fastify - PostgreSQL and an ORM: schema design, migrations, and query optimization - REST API design, JWT authentication, and role-based access control - Payment gateway integration including webhook handling (Stripe, PayPal, WeChat Pay or similar) - Experience handling failure in multi-step transactions: downstream calls that time out without telling you whether they succeeded, idempotency keys, partial success, and compensating actions rather than rollback - Production operations experience with Docker, CI/CD and at least one cloud platform — you have deployed, monitored and debugged live systems yourself - Working React knowledge, enough to build and modify admin interfaces - A track record of joining a large existing codebase and becoming productive in it quickly PREFERRED QUALIFICATIONS — the higher up the list, the more it counts - High-volume transactional systems — e-commerce, payments, marketplaces or similar — and the queue, caching and database-performance judgment that comes from running one - Prometheus, Grafana and Loki; alert design and on-call experience - BullMQ, Redis or Valkey; distributed locks and horizontal scaling patterns - Payment reconciliation, settlement or chargeback experience - Saga or orchestration patterns for distributed transactions - React Native with Expo and EAS Build, with apps shipped to the App Store and Google Play PROJECT DETAILS - This is a part-time engagement: 20-25 hours per week, ongoing. We are looking for a long-running relationship (12+ months), not a one-off project - It is intended to grow. After launch this can become a full-time contract, or a permanent role, if it suits both sides - We are looking for someone in Metro Vancouver or the Greater Toronto Area. Work is remote, with an optional desk in our Richmond, BC office if you are in Metro Vancouver - Async by default, with one live window that works naturally with our China team: late afternoon Pacific is the following morning in Beijing HOW TO APPLY Please include in your proposal: 1. Links to work we can look at: GitHub, live products you built or ran, or technical writing. If your strongest work is under NDA, tell us what it was and what you personally owned instead — we do not expect a public repo for proprietary backend work. 2. Your city and province, and your available hours per week. We read every proposal and reply to the ones that answer both. Please answer the screening questions properly — that is what we shortlist on.