Mid-Level Full Stack Developer

Our Story

This is Undefined (https://thisisundefined.com) is a small London-based product studio working together with forward-thinking companies across a range of different sectors. All ideas are different and we treat them that way. We love creating digital products with a purpose and are looking for someone to join us so we can continue our mission.

About the role

We’re looking for a Full-Stack JavaScript Developer who enjoys working across both backend and frontend — someone comfortable in Node.js but equally happy crafting great user experiences in the browser. This is an initial 6-month fixed-term role, with the potential to extend or become permanent.

You’ll work end-to-end on projects: from shaping ideas, building out features, integrating services and APIs, through to testing, iterating and shipping. You’ll contribute to both client work and internal product development, and have plenty of space to learn, explore and grow as the team grows.

Our current stack includes Typescript, React (/Native), Next.js (& sometimes nuxt.js) + Nest.js. On the backend, we work with Node.js and modern tooling to build reliable, scalable, human-focused products.

We welcome the use of AI tools to support development — but we value thoughtful engineering and understanding of the code being produced. Independent thinking is important to us; we see AI as an assistant, not a replacement.

We’re a small, friendly team, so finding the right culture fit matters as much as your technical skills.

Responsibilities

• Design, build and maintain scalable Node.js backends and modern JavaScript / TypeScript services
• Help with frontend features (React / React Native) when needed
• Build robust API integrations, authentication flows and secure data handling
• Work with SQL and/or NoSQL databases, ensuring performance, reliability and optimisation
• Write well-tested, maintainable code, contributing to quality through automated testing and CI/CD practices
• Collaborate with the team to shape features from idea through to build, testing and iteration
• Support both client and internal projects, contributing to technical decisions and best practices

About you

• Have multiple years of professional development experience, ideally working on live production systems
• Strong experience with Node.js and modern JavaScript / TypeScript
• Comfortable integrating APIs and working with authentication / security workflows
• Ideally have 1–2 years agency or multi-project experience (or similar exposure to varied projects)
• Positive, collaborative and proactive mindset
• Confident, professional and curious, with a desire to keep learning

Location

This is a hybrid role. The current split is 1-2 days per week in our office, in Bethnal Green, the remaining is remote, although you're always welcome in the office if you prefer.

Job Type

Full-time, Fixed term contract, Temp to perm

Salary

£45,000 - £55,000 per annum.

Benefits

• Casual dress
• Company pension
• Flexitime
• Work from home

Ability to commute/relocate

• London E2: reliably commute or plan to relocate before starting work (required)

Language

• English (required)

Work authorisation

• United Kingdom (required)

Come and join us! Please apply with availability.