Senior Performance Engineer (all genders)

Your high speed mission About Speed Kit Slow websites suck! Of 3.5 hours you spend online each day, 20 minutes are wasted waiting for websites to load. In your life, you will waste one whole year. Join our mission of building a web without loading times to make all Internet users happier. Our product Speed Kit is the all-in-one page speed tool and accelerates websites worldwide, including market leading companies like BMW, Zwilling and GANT. Our world-class team uses the latest web technology trends to make our customer websites up to 4x faster and to improve the user experience for 300 million users per month. Sounds exciting? Come on board and help us so that no one has to suffer from lost time! We have many exciting ideas for taking Speed Kit to the next level, that’s why we are currently looking for further addition as a Performance Engineer (all genders) in full time (40 hours). About Your Role Our Product Integration team sits at the intersection of performance engineering and customer architecture. The goal of the team is to ensure every customer extracts maximum value from Speed Kit's caching and preloading engine, and you are the hands-on technical expert who makes that happen. You will start each engagement by diving deep into the customer's stack, analyzing real-world user data (RUM) to identify critical rendering path bottlenecks. From there, you will adapt Speed Kit to solve those limits—whether that means extending our Service Worker capabilities, seamlessly integrating with complex frontend state, or developing advanced delivery strategies for highly dynamic content. Your impact scales beyond the individual customer. The custom solutions and architectural patterns you build on the front lines feed directly back into our core product roadmap. You will prototype new features, build automated tooling for our CI/CD pipelines, and future-proof our integrations when enterprise customers undergo major architectural shifts (e.g., migrating from MPAs to SPAs). In short, you are the technical bridge between our core engine and the wild, untamed reality of the web. About your potential tasks Complex Integrations: Architect and deploy highly adapted Speed Kit implementations, leveraging our Bloom filter-based cache invalidation and manipulating network requests on the fly. Frontend Problem Solving: Engineer custom JavaScript solutions to handle tricky edge cases like broken slider frameworks, flicker control during HTML merges, predictive preloading collisions, and lazy-loading race conditions. Product Prototyping: Distill your custom client solutions into native core product features, acting as a crucial feedback loop for our core engineering team. Scalable Tooling: Develop sophisticated internal and external tooling to automate the integration lifecycle, infrastructure maintenance, and QA validation. Deep Architectural Analysis: Audit complex e-commerce architectures for Core Web Vitals bottlenecks (LCP, CLS, INP) and UX regressions using our Real User Monitoring (RUM) stack. Your ticket for our spaceship We care deeply about your engineering fundamentals and your drive to untangle complex systems, not your formal degrees. To thrive in this role, you need: To Be A Web Fundamentalist: You know how the web actually works under the hood. We need deep, practical knowledge of Vanilla JavaScript, the DOM, browser rendering pipelines, and HTTP network layer. (If you only know how to write React components, this isn't the role for you). To Be Battle-Tested: You have a strong background in frontend development, ideally navigating the messy realities of e-commerce stacks or agency client work. You are comfortable rapidly switching contexts between different architectures. Service Worker & Caching Expertise: You understand Service Worker lifecycles, scope limitations, and complex caching strategies (e.g., stale-while-revalidate), and you know how to debug them in production. A Data-Driven Mindset: You don't guess; you measure. You understand the difference between synthetic lab data and field data (CrUX/RUM) and use analytics to prove the business value (conversion rate uplift) of your technical optimizations. Why get in? Remote-first: You can work 100% remote within Germany, if you want to We set you up with your office work station from screen to office chair Pick your OS: You can freely choose your OS between Mac, Windows or Linux Beautiful office: Work in the heart of Hamburg’s Schanzenviertel Pet-friendly office: You’re always welcome to bring a furry friend Awesome coworkers: Join a competent, humorous crew Flexible work: Work on a full-time or part-time schedule Flat hierarchies: The best ideas win, no matter by whom Event slots: Several times a year you can vote on what to do - haven't you always wanted to go karting with your colleagues? Vote for it! Speed.Fest: Every quarter we all get together at our HQ in Hamburg for workshops, good food, events and a great time. Personal training budget: We help you to grow your career and skills Future-proof pension scheme: feel free to bring your pension scheme with you or let our experts advise you Countdown 6️⃣ … You share your CV or LinkedIn profile with us 5️⃣ … We schedule a first (video-) call (15~30 minutes) 4️⃣… We schedule a 1st technical interview to get you in contact with the team (30~60 minutes) 3️⃣… We send you a (coding-) case to prepare for our 2nd meeting 2️⃣… We schedule a 2nd technical interview to talk about the (coding-) case (90~120 minutes) 1️⃣… If both sides are happy, we will prepare the contract …0️⃣ You join our rocket ship! Your contact person Simon is happy to receive your application and is available for your questions @