Senior iOS SDK Engineer

Senior iOS SDK Engineer About CloudX At CloudX we’re building a new supply-side advertising platform for mobile publishers. We’re convinced that an AI-native product will significantly advance the state of the art in mobile advertising; we recently raised a $30M Series A in order to bring this dream to life. We have a long history of innovation in this space — our founding team previously built MoPub (sold to Twitter for $350M) and MAX ( acquired by AppLovin ). Our new platform combines real technical improvements like verifiably fair auctions with a truly AI-native product experience to give publishers unprecedented control over their ad monetization strategy. About The Team Our Engineering team is distributed and remote — spanning UTC-8 to UTC+6, with core working hours of roughly the US Eastern business day. We have a strong ownership culture and are heavily collaborative, relying primarily on asynchronous, written, communication for coordination. We ship daily and believe that fast CI and good test coverage is the best way to remain productive as we scale. We’re small and high trust; we optimize for rapid iteration and experimentation. Everyone has access to the latest AI tools, but rather than generating vibe-slop we use them pragmatically to build better products. We are lucky to work closely with our talented Product and Business teams to make sure we’re building the right things. It’s a true early-stage startup with lots of important work to go around. What you'll do The Mobile team builds the core infrastructure that will power revenue for thousands of mobile apps. At scale, our SDK will run in production apps with hundreds of millions of daily active users, processing billions of ad requests per month. We're a small, high output team committing code daily. You'll own the critical path. The SDK is the first point of contact between publishers and CloudX's marketplace, so reliability and performance aren't optional. Every line of code you write affects real revenue for real businesses. We move fast, ship often, and measure everything. As a Senior iOS SDK Engineer, your key responsibilities will be to: Collaborate with the product team to design and implement core SDK features Build and maintain integrations with third-party ad networks (Meta, Google AdMob, etc.) Optimize SDK to be seamless in host apps: minimize startup impact, reduce binary size, manage resources efficiently, and handle errors gracefully without affecting app stability Engage directly with publishers to diagnose real-world issues and improve SDK usability, reliability, and integration experience Who you are We encourage you to apply if you meet these requirements: Proven experience building and maintaining production iOS apps or SDKs Strong proficiency in Objective-C (Swift experience a plus) Expert-level understanding of iOS concurrency (GCD, async/await, threading, memory management) Deep understanding of iOS internals: runloops, networking, background execution, app lifecycle Strong testing and debugging discipline A genuine builder: Someone who codes daily, sweats the details, and has shipped complex systems, not just talked about them. You get energy from solving hard engineering problems yourself. A clear, concise, communicator: You can take a messy problem and make it legible, explaining trade-offs to engineers, PMs, and execs without hand-waving. A startup operator with good instincts: You know when to ship fast, when to slow down, and how to navigate ambiguity without waiting for perfect specs or marching orders. An owner, not a passenger: You turn loosely defined problems into real solutions, care deeply about whether the product actually works, and use AI as a force multiplier, not a crutch. While not required, we’re particularly interested in candidates with: Experience building developer-facing SDKs or libraries, including documentation, versioning, and integration support Experience distributing SDKs via CocoaPods / Swift Package Manager / binary frameworks Cross-platform SDK experience with Flutter, React Native, or Unity development Mobile advertising experience: Understanding of ad mediation, waterfalls, etc. In general, we’re looking for people with grit, passion, and talent. If you’re not sure if this role is an exact fit, we encourage you to apply. Many members of our team have had interesting career paths and we relish the chance to work with extraordinary individuals. Pay and Benefits The annual US base salary range for this role, and other engineering roles, is $150,000 – $300,000. This salary range is broad in order to accommodate a wide range of candidates; the interview process will narrow it down based on a number of factors, including your experience, qualifications, and location. We offer equity compensation and top-tier medical, dental, and vision benefits. We also have a generous hardware budget for a computer, monitor, and other core equipment necessary to work effectively on a remote team. We care about the quality of your work more than the specific hours you spend getting it done, and try to minimize the number of synchronous meetings in favor of greater flexibility. There is no in-office requirement.