Senior Backend Engineer

Company Description WireMock is the industry standard for API environment simulation. With a massive global open-source footprint and deep adoption across the Fortune 500, we provide the critical infrastructure that engineering teams use to de-couple development from fragile dependencies. As AI agents and LLM-integrated apps redefine the SDLC lifecycle, WireMock is building the simulation layer required to develop, test, and onboard at the speed of autonomous code. We’re leveraging our massive OSS pedigree to scale a SaaS/Cloud platform that handles the complexity of the modern, distributed enterprise. The role The company is spread between the UK, California and the US east coast, with the engineering team based in London. This position will be hybrid and you will be required to arrive two days a week to the London office. We’re looking for someone who: Wants to work in a small, dynamic team Likes working in a product-driven engineering environment, wearing multiple hats and actively contributing to product design. Has integrated AI coding tools into their workflow, but can reason and function without them where necessary. Cares about user delight over technical purity. Writes code in Java, Kotlin and ideally Javascript. Enjoys contributing to open source, including writing and speaking. Proactively improves their own skills and understanding of the domain they’re working in Salary range £80k-110k. Java/Kotlin Product Engineer We’re looking for a Java/Kotlin developer who has a solid understanding of networking and HTTP, experience building complex web applications and an eye for quality balanced by pragmatism about delivery. The right candidate will have a disciplined approach to code quality and be comfortable using TDD, trunk-based development and continuous integration/delivery practices. They’ll also have the desire to gain a deep understanding of the product and its customers, and the ability to contribute to product design decisions. They’ll also want to write and speak to our community about the product, API mocking and related topics. Design, build, test and support backend features in the commercial SaaS product. Create, maintain and support cloud infrastructure. Write documentation, contribute to article/tutorial content. Embed AI processes and usage across the SDLC Contribute to the WireMock open source projects. Help customers and community members with technical queries. On call out-of-hours, approximately one week in every six Requirements At least 6 years professional software development experience, of which the majority should be in Java or another JVM language. Recently written production code in Kotlin. Demonstrable experience using AI coding agents such as Claude Code, GitHub Copilot or Cursor on real projects. Solid understanding of TCP/IP and HTTP. Solid understanding of RESTful API design. Experience working at least one mainstream SQL database in a production application. Basic familiarity with Docker. Fluent spoken and written English. Able to work autonomously and take initiative when remote. UK based and required to work in London 2 days per week Nice-to-haves Experience developing against AWS services – ECS, EC2 and RDS in particular. Experience managing cloud infrastructure via configuration-as-code. Front end development experience - HTML, CSS and Javascript. Experience with gRPC, GraphQL or websockets development. Interview Process Our process is streamlined and personal. You will connect with the Head of Product, the engineering team and th CEO as we look to make a decision quickly.