Backend Engineer (Kotlin)

Synthesized; Greater London; Hybrid; GBP 70,000 - 120,000; Full time

Benefits offered by this job

Competitive salary

33 days annual leave

Hybrid work in London/NY offices

Learning & development budget

Private medical, dental, and vision

Job summary

Synthesized is redefining software testing with agentic AI and is hiring a Backend Engineer (Kotlin) to scale the control-plane of its fast-growing SaaS platform.

As part of a lean, high-impact team, you’ll design scalable Spring Boot services, build robust data models in PostgreSQL, and help shape architecture with CI/CD workflows and collaboration with Product and Frontend.

Qualifications

• Shipped Kotlin/Java services with Spring Boot in production.
• Strong PostgreSQL knowledge, schema design and migrations.
• Familiar with jOOQ, Liquibase and type-safe data layers.
• Writes clean, testable code with good test coverage.
• Hands-on with OpenAPI and codegen workflows.

Responsibilities

• Build and maintain scalable Spring Boot services in Kotlin.
• Design and evolve data models in PostgreSQL and migrations with Liquibase.
• Co-own and enforce OpenAPI contracts across teams.
• Practice shift-left testing with JUnit, Testcontainers, MockMVC.
• Contribute to CI/CD workflows with GitHub Actions.

Skills

Kotlin

Spring Boot

OpenAPI

PostgreSQL

JUnit

Testcontainers

CI/CD

GitHub

Distributed systems

Tools

Liquibase

jOOQ

OpenAPI codegen

Docker

Kubernetes

GitHub Actions

Job description

About Us

It's hard to build a reliable system. It's harder to make sure that what you've built is really reliable.

Synthesized is redefining software testing with agentic AI. Our platform automates test data, test cases, and test environments - empowering enterprise teams to ship faster, reduce compliance risks, and modernise QA at scale.

Our products are used by some of the world's leading organizations, such as Deutsche Bank, UBS, the European Commission, and others.

We’re an ambitious VC-backed startup, having just gone through Series A with leading global investors including IQ Capital, Seedcamp, and Deutsche Bank. We have ambitious growth plans for 2025, and we are so keen for you to join us on the journey.

The Role

We're hiring a Backend Engineer (Kotlin) to help scale the control-plane of our fast-growing SaaS platform.

As customer adoption accelerates, we’re expanding the core platform to support new features, better performance, and rock-solid reliability. You’ll join a lean, high-impact team, reporting to the Backend Team Lead, and work closely with Product and Frontend to deliver end-to-end value.

This is a hands-on role with plenty of ownership - perfect for someone who wants to shape architecture, build resilient systems, and make their mark on a product used by teams around the world.

What You’ll Do

• Build and maintain scalable Spring Boot services in Kotlin, with clean architecture and fault tolerance in mind.
• Design and evolve data models in PostgreSQL, manage schema migrations via Liquibase, and work with jOOQ for type-safe access.
• Treat OpenAPI contracts as a source of truth - co‑own and enforce across teams, enabling automated code generation.
• Practice shift‑left testing with solid test coverage (JUnit, Testcontainers, MockMVC).
• Contribute to a documentation‑as‑code culture - writing clear docs alongside new features.
• Help shape and refine our CI/CD workflows with GitHub Actions.
• Collaborate daily with Product, Design, and Frontend to clarify stories and deliver iteratively.
• Participate in code reviews, mentor others, and contribute to architectural discussions.
• Monitor production systems, triage incidents, and bake learnings back into the system.

About You

• You’ve shipped Kotlin (or Java) services with Spring Boot in a production environment.
• Strong with PostgreSQL - comfortable with schema design, indexing, and migrations.
• Familiar with jOOQ, Liquibase (or similar), and value type safety in data layers.
• You write clean, testable code and understand the value of good test coverage.
• You’re hands‑on with OpenAPI and codegen workflows, and like well‑defined API contracts.
• Experience with GitHub, CI/CD pipelines, and cloud‑native principles (containers, observability, REST/gRPC APIs).
• You understand how to build resilient distributed systems - bonus points for JVM tuning experience.
• Some frontend awareness or full‑stack curiosity is a nice plus.
• Strong communicator, comfortable working across disciplines and explaining technical decisions clearly.
• Always learning, always improving. You care about clean code and delivering value in small, fast iterations.

What We Offer

• Competitive salary and meaningful equity
• 33 days annual leave (including flexible national holidays)
• Hybrid, flexible working from our London or New York office (3 days/week in our office space in Shoreditch)
• Learning & development budget for coaching, courses, and conferences
• Private medical, dental, and vision cover
• Regular team socials and offsites
• Working with a team that’s smart, ambitious, and deeply collaborative
• Generous Family leave

Equal Opportunities

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