Full-Stack Developer

On On Technology Services Limited; Hong Kong Island; On-site; HKD 420,000 - 660,000; Full time

Job summary

On On Technology Services Limited is seeking a mid-level Full-Stack Developer to build mobile apps and web products for our clients end to end, covering front end, back end, and database work.

You will ship React Native mobile apps, Next.js web products, and manage databases and APIs while collaborating with designers to turn Figma concepts into production-quality interfaces and maintaining what you ship.

Qualifications

• 3–5 years of professional development experience.
• Production apps with React Native.
• Experience building web products with Next.js and TypeScript.
• Good knowledge of backend databases (PostgreSQL, MySQL, Firebase, Supabase, or similar) and API design.
• Ability to work across the full stack and own a feature from database to UI.

Responsibilities

• Build cross-platform mobile apps in React Native.
• Build web products in Next.js and TypeScript.
• Design and work with backend databases: schema design, queries, migrations, and performance.
• Build and integrate APIs, authentication, and third-party services.
• Work closely with designers to turn Figma files into production-quality interfaces.
• Deploy, monitor, and maintain what you ship.

Skills

React Native

Next.js

TypeScript

APIs

Database design

Tools

PostgreSQL

MySQL

Firebase

Supabase

OpenAI API

Claude Code

Cursor

Job description

On On Technology Services Limited is looking for a full-time, mid-level Full-Stack Developer to join our team. You will build mobile apps and web products for our clients end to end, covering front end, back end, and database, and help us win new work by putting working demos in front of potential clients.

What you\'ll be doing

Build cross-platform mobile apps in React Native

Build web products in Next.js and TypeScript

Design and work with backend databases: schema design, queries, migrations, and performance

Build and integrate APIs, authentication, and third-party services

Work closely with our designers to turn Figma files into production-quality interfaces

Deploy, monitor, and maintain what you ship

Demos and pitches (secondary)

Build quick working prototypes and proof-of-concepts for potential clients

Prepare and walk through technical demos in client meetings

Turn client ideas into something clickable fast, so we can validate scope before full development

What we\'re looking for

Around 3–5 years of professional development experience

Solid experience shipping production apps with React Native

Solid experience building web products with Next.js and TypeScript

Good knowledge of backend databases (PostgreSQL, MySQL, Firebase, Supabase, or similar) and API design

Ability to work across the full stack and own a feature from database to UI

Comfortable with AI-assisted development, or "vibe coding", using tools such as Claude Code, Cursor, or similar, while still reviewing and understanding every line you ship

Speed and pragmatism: able to produce a convincing demo in days, not weeks

Clear communication, including explaining technical decisions to clients and non-technical stakeholders

Strong attention to detail and the ability to manage multiple projects to deadline

Nice to have

Experience integrating AI and LLM APIs (Gemini, OpenAI, OpenRouter, or similar)

Experience with cloud and deployment platforms (AWS, Vercel, or similar)

Experience with Flutter or native mobile development

Experience working directly with clients in an agency or studio environment

What we offer

Competitive salary based on experience

Varied client projects across mobile, web, and AI

Freedom to use modern AI development tools in your daily workflow

A collaborative team that values your technical input

Flexible working arrangements, open to discussion

About us

On On Technology Services Limited (OnOn Technology) is a Hong Kong software studio. We build mobile apps, web platforms, and AI systems for businesses, combining fast delivery with production-quality engineering.