Principal Engineer, iOS Performance

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.   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.   BENEFITS AND MORE We’re offering a salary of £60,000 – £80,000, plus an additional 10% of your salary awarded to you in shares each year. These awarded shares will become yours in yearly instalments over the next three years, and you can choose to either sell them or keep them as shares. And you'll receive 28 days holiday, plus bank holidays and comprehensive private medical cover.  That’s not all. You'll be enrolled in our pension scheme, where our standard contributions are 7% and employee contributions are 5%. We also have comprehensive private medical cover, enhanced family leave provisions, a car salary sacrifice scheme, share-save options, and much more.   We always want to give you the support you need and help prioritise your wellbeing, that’s why we provide access to 24/7 online GP and dentist, as well as specialist support for assisted fertility, gender dysphoria, menopause, period care plans and lots more.   On top of all that, our hybrid model, Connected Working, combines the best of both worlds – office and home working. You'll spend a minimum of 3 days a week in the office with your team, focused on collaboration and connection. Additionally, we have our remote-first periods at set times during summer and winter. During these periods, you can work remotely anywhere in the UK and from certain locations abroad. Discover more about our hiring process and explore our Engineering Blog. #LI-EC1 #LI-Hybrid

Reddit is a community of communities. It’s built on shared interests, passion, and trust, and is home to the most open and authentic conversations on the internet. Every day, Reddit users submit, vote, and comment on the topics they care most about. With 100,000+ active communities and approximately 126 million daily active unique visitors, Reddit is one of the internet’s largest sources of information. For more information, visit www.redditinc.com. The Content Ecosystem organization fuels Reddit's contribution flywheel by integrating posting, commenting, community building, and professional platforms into interlocking growth loops. We lower the friction required to create content and guide new communities from day zero to a thriving state. Additionally, we consolidate professional presence into a trusted hub for creators while serving as the foundational shield for platform data defense and safety mandates. Ultimately, our goal is to move Reddit beyond consumption-only usage, driving daily active user growth by turning passive lurkers into meaningful contributors. We need a web client and mobile consumer product domain expert to lead the architectural overhaul of our post and comment composers across all platforms. As a Senior Staff Engineer, you will define the multi-year technical vision for how users create content on Reddit. You will focus on continued modernization of our composers and building out new contribution formats, particularly the future of video creation and editing. By removing client-side friction, integrating intelligent posting/commenting user empowerment, and setting the standard for client performance, you will be the technical cornerstone for accelerating our global user contribution and content ecosystem growth. KEY RESPONSIBILITIES: * Architect for Scale: Define and execute the org-wide client architecture strategy to support seamless video creation, editing, and uploading directly within our shared composers. Establish the patterns for how all future formats integrate into the client layer. * Accelerate Product Roadmap: Build and scale new contribution formats natively within the shared post and comment experiences. Unblock execution for high-upside strategic bets designed to reduce identity-risk barriers for sensitive content and productize viral, low-effort creation formats that convert passive consumers into active contributors. * Mentorship & Org Leadership: Serve as the technical anchor for the Contribution engineering team and influence the broader Content Ecosystem org. Translate complex product requirements into actionable technical roadmaps and drive alignment across Web, iOS, and Android platforms. * Leverage Modern Tooling: Thoughtfully utilize AI-assisted development tools to accelerate prototyping, system design, and coding, while applying rigorous judgment to validate and own the final outputs. Evangelize AI as a tool. * Optimize Contribution Funnel: Lead the engineering of highly performant client infrastructure. You will tackle challenges like zero-latency rich-text rendering, resilient edge-optimized media upload pipelines, and complex state synchronization for offline and online editing to maximize global contribution success rates. QUALIFICATIONS: * 10+ years of professional software engineering experience with a proven track record as a Senior Staff Engineer or Principal Engineer on consumer-facing mobile or web client applications. * Client Architecture Expertise: Deep mastery of modern web architecture (e.g., React, TypeScript, advanced state management) with strong architectural command of native mobile paradigms (iOS/Swift, Android/Kotlin) to define unified client APIs and lead cross-platform engineering standards. * Domain Expertise: Demonstrated track record of solving hard client-side performance and rendering bottlenecks at scale, building highly interactive features such as zero-latency rich-text editors, asynchronous media processing pipelines, or real-time state synchronization systems. * Communication: Exceptional written and verbal communication skills. Ability to influence VP-level technical direction and navigate strict tradeoffs between performance, reliability, and business impact without directly managing the engineers involved. * Demonstrated ability to lead large, cross-functional engineering initiatives that balance technical excellence with aggressive growth targets. Benefits: * Comprehensive Healthcare Benefits and Income Replacement Programs * 401k with Employer Match * Global Benefit programs that fit your lifestyle, from workspace to professional development to caregiving support * Family Planning Support * Gender-Affirming Care * Mental Health & Coaching Benefits * Flexible Vacation & Paid Volunteer Time Off * Generous Paid Parental Leave      Pay Transparency: This job posting may span more than one career level. In addition to base salary, this job is eligible to receive equity in the form of restricted stock units, and depending on the position offered, it may also be eligible to receive a commission. Additionally, Reddit offers a wide range of benefits to U.S.-based employees, including medical, dental, and vision insurance, 401(k) program with employer match, generous time off for vacation, and parental leave. To learn more, please visit https://www.redditinc.com/careers/. To provide greater transparency to candidates, we share base salary ranges for all US-based job postings regardless of state. We set standard base pay ranges for all roles based on function, level, and country location, benchmarked against similar stage growth companies. Final offer amounts are determined by multiple factors including, skills, depth of work experience and relevant licenses/credentials, and may vary from the amounts listed below. The base salary range for this position is: $232,500—$325,500 USD In select roles and locations, the interviews will be recorded, transcribed and summarized by artificial intelligence (AI). You will have the opportunity to opt out of recording, transcription and summarization prior to any scheduled interviews. During the interview, we will collect the following categories of personal information: Identifiers, Professional and Employment-Related Information, Sensory Information (audio/video recording), and any other categories of personal information you choose to share with us. We will use this information to evaluate your application for employment or an independent contractor role, as applicable.  We will not sell your personal information or disclose it to any third party for their marketing purposes.  We will delete any recording of your interview promptly after making a hiring decision.  For more information about how we will handle your personal information, including our retention of it, please refer to our Candidate Privacy Policy for Potential Employees and Contractors. Reddit is proud to be an equal opportunity employer, and is committed to building a workforce representative of the diverse communities we serve.  Reddit is committed to providing reasonable accommodations for qualified individuals with disabilities and disabled veterans in our job application procedures. If, due to a disability, you need an accommodation during the interview process, please let your recruiter know.