Back End Developer (Kotlin)

Synthesized — London, GB
Published on

About Us

Synthesized is transforming how the world tests software with AI. Trusted by global leaders like Deutsche Bank, UBS, and the European Commission, our AI-powered platform enables teams to generate high-quality test data and test cases in seconds, thereby slashing costs, accelerating delivery, and eliminating reliance on production data. We are a VC-backed company with strong traction across financial services, healthtech, and telecom, and a $90B+ market in sight as we scale fast into 2025 and beyond.

The Role

We’re looking for a Back End Developer (Kotlin) to evolve and scale the control-plane of our SaaS platform. Reporting to the Backend Team Lead, you will design and maintain services that power everything the UI depends on. You’ll collaborate closely with Product Management on feature design, ensuring that new features meet customer needs and expectations. This role offers the opportunity to shape system architecture, own features end-to-end, and make key architectural decisions that push our product forward.

Key Responsibilities

  • Design, implement, and maintain Spring Boot services in Kotlin with a focus on clean architecture and resilience.
  • Model data in PostgreSQL and own schema migrations with Liquibase; access data through jOOQ.
  • Treat the OpenAPI contract as the single source of truth and enforce it across teams to automate server/client generation.
  • Write unit and integration tests alongside your code, practicing shift-left testing.
  • Contribute to the CI/CD workflow on GitHub Actions.
  • Collaborate daily with the Product Manager, Team Lead, and frontend engineers to clarify stories and deliver iterative value.
  • Participate in code reviews and architecture discussions, mentoring where possible.
  • Help monitor production using logs/metrics, triaging incidents, and integrating learnings back into design and tests.

About You

  • Professional experience building Kotlin (or Java) services on Spring Boot in production environments.
  • Solid knowledge of PostgreSQL schema design, SQL queries, and migration tools like Liquibase; fluency with jOOQ or similar tools.
  • Comfortable writing tests (JUnit, Testcontainers) and using code-coverage metrics.
  • Familiar with OpenAPI / Protobuf for typed contracts between services and UI.
  • Experience with CI/CD using GitHub Actions or similar.
  • Understanding of cloud-native patterns and the pitfalls of distributed systems, particularly relevant to our topology.
  • Hands-on experience with performance profiling and JVM tuning is a plus.
  • A strong communicator who can explain technical concepts to diverse audiences and enjoys collaborative brainstorming.
  • Continuous learner committed to clean code and iterative delivery.

What We Offer

  • A hybrid work arrangement with 3 days in our wonderful office located in the heart of Shoreditch.
  • Competitive cash compensation plus share options.
  • Flexible work hours and a personal development budget covering coaching, courses, and events.
  • Comprehensive health, vision, and dental plan coverage.
  • 33 days of paid leave annually, including flexible national holidays.
  • Weekly snacks and drinks, fostering a great workplace culture.
  • Opportunities for company events, team socials, and international trips.

Equal Opportunities

At Synthesized, we are committed to creating an inclusive and diverse workplace. We are an equal opportunity employer and do not discriminate against applicants based on race, ethnicity, color, ancestry, national origin, religion, sex, sexual orientation, gender identity, age, disability, veteran status, genetic information, marital status, or any other legally protected status.

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