• Design, build, and maintain a modular Swift SDK used by developers across Apple platforms • Work on crash reporting, hang detection, performance monitoring, and telemetry instrumentation • Build reliable mechanisms for offline storage, batching, retries, and data delivery under mobile runtime constraints • Contribute to SDK architecture, API ergonomics, and backward compatibility • Design and evolve APIs with a focus on stability, clarity, and long-term compatibility • Debug complex issues across devices, OS versions, and app environments, including threading, memory, and lifecycle challenges • Develop and maintain capture services for networking, user interactions, and system events, leveraging frameworks such as MetricKit • Optimize startup performance, binary size footprint, memory usage, and thread safety • Coordinate with cross-platform SDK teams (React Native, Flutter, Unity) to ensure native SDK changes do not introduce downstream breaking issues • Collaborate on OpenTelemetry alignment and upstream contributions • Partner with Product and Customer Success to incorporate developer feedback

• Build and maintain feature-rich iOS applications. • Develop intuitive user interfaces to simplify athlete data input and visualisation. • Collaborate cross-functionally with Product, Design, and Sports Science teams to design new features. • Write robust, well-tested, and maintainable code. • Participate in the full product lifecycle, from prototyping to release. • Contribute to improving team processes, tooling, and architecture.

• Collaborate with team members to build meaningful products. • Take risks and lift each other up in the development process. • Ensure high-quality engineering practices in project outcomes. • Use AI to help clients achieve bigger outcomes.

In Dr Joseph Lstiburek’s essay “A Perfect Wall”, he analyzes the elements that enable a wall to perform its core function–separating the inside from the outside. He calls the most solid type of wall a “five hundred year wall”, referring to the five centuries of construction knowledge that went into its making (and the five hundred years it could endure). Capacity accumulates across generations, bringing perfection within reach. Randy Williams’ “A Practical Perfect Wall” takes Lstiburek’s ideal principles of wall-building and clearly outlines modern procedures for making them into real walls. A perfect wall and perfect code are similar. In applying best practices, we experience perfection not as a mystical ideal, but as a practical exercise of our expertise. Perfection is not about pushing a meaningless metric to 100%. Code is perfect when it achieves its intended purpose. We are looking for a highly competent engineer with a deep appreciation for the practical perfectibility of everyday, tangible experience, and a desire to make constant improvements over time. Someone who shares our standards for a perfect system: one that is built with a specific end use in mind, and reliably fulfills that need. The engineering team at Co-Star values communication, collaboration–and most importantly, delivery. We prioritize making as much contact with reality as possible, to find out directly from users what they want and need. Like walls make buildings that hold human life within them, the systems we create together are containers of intimacy, humor and connection. What you'll do You’ll release features weekly to millions of people. Every launch is an experiment in making astrology feel more accessible, and your work will be in users’ hands almost immediately. You’ll collaborate closely with product and design to turn ambitious concepts into practical, reliable code. We’re a small, nimble team: you won’t just be handed tickets, you’ll have real input into how we build and you’ll influence the future of our iOS codebase. What we offer Fully covered $0 deductible healthcare + vision, dental, and therapy 401(k) + 5% matching Unlimited vacation + 2 week company-wide recharge at the end of each year Equipment budget 12 weeks 100% paid parental leave Readings with in-house astrologers A competitive total rewards package, including base salary, equity (stock options), and benefits. Our salary and equity ranges are highly competitive within the tech industry and are regularly updated using the most reliable compensation survey data. Offers are crafted based on a candidate’s experience, expertise, location, and internal equity relative to peers. Our target new hire base salary ranges for this role is $135,000-$190,000.