Senior Fullstack Developer — Java or Kotlin, React and TypeScript in London

Founded in Switzerland in 1968, Zühlke is owned by its partners and located across Europe and Asia. We are a global transformation partner, with engineering and innovation in our DNA. We're trusted to help clients envision and build their businesses for the future – to run smarter today while adapting for tomorrow’s markets, customers, and communities. Our multidisciplinary teams specialise in tech strategy and business innovation, digital solutions and applications, and device and systems engineering. We excel in complex, regulated spaces including health and finance, connecting strategy, tech implementation, and operational services to help clients become more effective, resilient businesses.

The role

As a Senior Fullstack Developer, you will be a hands-on member of a high-performing engineering squad, building and operating business-critical digital services. This is a backend-led fullstack role. You will use Kotlin or modern Java, ideally Java 17 or later, together with the wider JVM ecosystem, to develop reliable services, APIs and event-driven workflows. You will also contribute to modern web interfaces using technologies such as React and TypeScript.

You will work in an increasingly AI-augmented engineering environment. We are looking for people who are curious about AI-augmented engineering and willing to experiment with tools that improve software delivery. You will not be expected to use AI tools every day, but you should be open to applying them where they provide clear value, while validating outputs for correctness, security and maintainability.

Working closely with product managers, designers and fellow engineers, you will turn product requirements into well-structured, maintainable and production-ready solutions. You will contribute throughout the delivery lifecycle—from technical discovery and implementation through to deployment, production support and continuous improvement. You will take ownership of significant features and services, contribute to technical decisions, support other engineers and help maintain high standards of engineering quality.

How you will make an impact

• Build and maintain reliable JVM-based services using Kotlin or modern Java.
• Design and develop well-structured APIs and integrations.
• Build reusable services, APIs and components that enable other teams to deliver consistently and reduce duplication.
• Contribute to API design standards, documentation and versioning across services.
• Deliver complete end-to-end features by connecting backend services and data models with responsive web interfaces.
• Use appropriate test-first and test-informed practices to create effective automated tests.
• Experiment with AI-assisted engineering tools where they provide clear value, such as exploring solutions, improving tests, documenting systems or investigating issues.
• Validate AI-assisted outputs for correctness, security, maintainability and suitability before they are used.
• Contribute to event-driven workflows and asynchronous processing using suitable messaging or streaming technologies.
• Participate in technical discovery, spikes, architecture discussions and peer code reviews.
• Improve build, test and deployment pipelines to support safe and efficient delivery.
• Embed structured logging, metrics and distributed tracing to make services easier to operate and troubleshoot.
• Consider the operational, security and governance implications of engineering decisions, particularly in complex or regulated environments.
• Identify and address technical debt, performance issues and reliability risks.
• Share knowledge, support collective code ownership and contribute to a collaborative, low-ego team culture.

What we are looking for

• Strong commercial experience developing server-side applications with Kotlin or modern Java, ideally Java 17 or later.
• Good knowledge of the JVM ecosystem and common backend development practices.
• Experience designing, building and operating APIs and distributed services.
• Understanding of service reliability, maintainability, performance and security.
• Proven experience writing effective automated tests.
• Practical experience with relational databases.
• Experience with modern frontend development, ideally using React and TypeScript.
• Familiarity with CI/CD practices and supporting software in production.
• Experience working collaboratively in an agile, product-focused engineering team.
• Curiosity about AI-augmented engineering and a willingness to develop new ways of working.
• A thoughtful approach to code quality, technical trade-offs and continuous improvement.

• Practical experience using AI-assisted development or productivity tools in a software engineering context.
• Event-driven architecture and messaging or streaming technologies.
• Experience with frameworks such as Spring Boot, Quarkus, Micronaut or Ktor.
• GraphQL or comparable API technologies.
• Cloud platforms such as AWS, Azure or GCP.
• Containerisation and orchestration using Docker and Kubernetes.
• NoSQL, caching or distributed data technologies.
• Experience choosing between relational, NoSQL and other persistence technologies.
• Workflow orchestration and modelling of long-running business processes using BPMN or comparable technologies.
• Experience building shared platforms, common services or greenfield technical foundations.
• API governance in a multi-team engineering environment.
• Observability practices covering logs, metrics and distributed tracing.
• Experience working in regulated, financial-services or high-throughput environments.
• Exposure to payments, transaction processing or other complex business domains.

What success looks like

• Deliver valuable, production-ready features with the squad.
• Build services and APIs that are reliable, reusable and easy for others to consume.
• Improve the reliability, performance and operability of the services you work on.
• Use emerging engineering tools thoughtfully and responsibly where they add value.
• Contribute constructively to technical decisions, API standards and code reviews.
• Help the team release software safely and efficiently.
• Support a culture of learning, collaboration and shared responsibility.

Working environment

You will work as part of a cross-functional engineering squad alongside product, design and delivery colleagues. The role is expected to remain substantially hands-on, with opportunities to influence technical direction and support the development of other engineers. The role may include working on-site with clients, collaborating directly with client stakeholders and delivery teams to understand their needs, shape technical solutions and support successful delivery. This may involve occasional travel or agreed on-site working, depending on the project and client requirements.

If you feel you don't meet all the requirements, we are still happy to get to know you, learn more about your ambitions and ideas and look forward to receiving your application! We welcome people from all backgrounds, regardless of their gender, personality, national origin, race, religion, colour, sexual orientation, gender identity, age, marital status, disability or veteran status.