Principal Mobile Apps Platform Engineer

About Autotrader

You’ve probably heard of Autotrader, but do you know what we’re all about?

We’re the UK’s leading automotive marketplace, a heritage brand, and a tech darling of the stock market. We bring together vehicle buyers and sellers to give them real choices. Cars may be what we're best known for but we’re also the place for pretty much everything else on wheels, from e-bikes to caravans.

In the automotive world, change is a constant, that’s why we take our job of untangling the complex car-buying journey very seriously.

At our core, we’re all about people. We go our own way while embracing diversity and celebrating our differences. We dedicate ourselves to the idea that we work better together.

Autotrader is a beautiful, surprising and vibrant place to work. We might not be for everyone, but we could be perfect for you.

About the role

As a Principal Software Engineer, you will play a key role in evolving the in-app experience for the UK’s #1 car buying app. The Autotrader app has been downloaded over 23 million times and consistently serves over 3 million monthly users, maintaining leading ratings of 4.8/5 on the App Store and 4.7/5 on Google Play. While our core focus remains on the consumer experience, our mobile apps team are currently instrumental in transitioning Autotrader into a platform where consumers can buy vehicles entirely online.

We’ve evolved beyond traditional native development approaches by adopting a Server-driven UI architecture. Our team has developed a custom client-side framework that dynamically renders data, context, and layout configurations served up from a federated backend REST API. In this role, you will provide technical leadership for this platform, driving architectural scalability, performance, and long-term maintainability across our mobile applications.

We’re a close-knit tech community where collaboration and knowledge sharing are at the core of what we do. Regular pair programming, code reviews, and stand-ups ensure that our engineers stay connected and aligned. As a Principal Engineer, you’ll play a visible, strategic role in driving system design and architecture decisions, mentoring team members, and helping our teams deliver high-quality solutions at scale for one of the UK's most used digital products.

We actively encourage AI-assisted workflows. Whether it's using GitHub Copilot to eliminate boilerplate or LLMs to bounce ideas around, we give you the tools to move faster and focus on the hard engineering problems.

What we're looking for

• You should be comfortable with the fact that most of your development time will be spent working on our backend Kotlin services to maintain and evolve our server-driven UI framework.

• Proven experience with Kotlin Multiplatform (KMP), Gradle, and Spring Boot.

• Experience building and supporting mobile applications; proficient user of the development toolset on at least one of these platforms (Swift, Xcode, and Instruments for iOS; Kotlin, Jetpack, Android Studio for Android).

• Strong understanding of unit testing, RESTful API design, and a commitment to refactoring and regression test automation.

• Experience mentoring and coaching engineers, with a proven ability to share technical expertise and advocate best practices across a team.