We’re looking for a Senior C++/iOS Engineer to join the Baldur squad within User Platform (UP). Baldur owns Spotify’s Session Management and Delegated Authorization domains—the systems that enable applications to securely obtain, use, and manage access tokens for hundreds of millions of users. In this role, you’ll help shape the technology that powers secure access across every Spotify client and third-party integration.  Your work will support engineers across Spotify building mobile and desktop experiences, platform teams, and third-party developers integrating with Spotify’s authorization platform. You’ll collaborate across disciplines to build secure, reliable, and scalable authentication experiences that have a direct impact on millions of people every day. WHAT YOU'LL DO Collaborate with a highly autonomous and supportive engineering squad responsible for Spotify’s delegated authorization and session management platforms. Design, build, and evolve critical infrastructure powering Spotify applications and partner integrations using shared C++ libraries and native Swift on iOS. Develop secure, reliable, and performant delegated authorization flows, including token issuance, refresh, revocation, and session lifecycle management across multiple platforms. Partner with client and backend engineers to integrate with core authorization services, token issuance, client registration, and token revocation. Improve how credentials and access tokens are securely stored and managed on-device while balancing security, reliability, and application performance. Contribute to the evolution of Spotify’s authorization frameworks, Spotify-specific implementations, enabling new platforms and product experiences. Drive technical improvements, share knowledge with teammates, and help shape the long-term technical direction of delegated authorization and session management. WHO YOU ARE You have strong proficiency in C++, along with experience building native iOS applications in Swift, or you're excited to develop your expertise in Swift while applying your C++ skills. You have experience designing, building, or maintaining security-sensitive systems such as authorization, authentication, token management, credential storage, or related platforms. You bring a systems-thinking mindset and enjoy solving complex engineering challenges that span client and backend technologies. You have a solid understanding of software architecture, secure system design, and modern authorization protocols such as OAuth 2.0. You approach problems thoughtfully, with strong attention to detail and a focus on building secure, reliable, and maintainable solutions. You communicate clearly and enjoy collaborating with engineers across multiple teams and technical disciplines. You have experience working with shared cross-platform codebases and understand how native platform layers interact with common C++ libraries. You enjoy working on large-scale distributed systems where your contributions improve experiences for hundreds of millions of Spotify users. WHERE YOU'LL BE This role is based in London or Stockholm. We offer you the flexibility to work where you work best! There will be some in person meetings, but still allows for flexibility to work from home. Spotify is an equal opportunity employer. You are welcome at Spotify for who you are, no matter where you come from, what you look like, or what’s playing in your headphones. Our platform is for everyone, and so is our workplace. The more voices we have represented and amplified in our business, the more we will all thrive, contribute, and be forward-thinking! So bring us your personal experience, your perspectives, and your background. It’s in our differences that we will find the power to keep revolutionizing the way the world listens.   At Spotify, we are passionate about inclusivity and making sure our entire recruitment process is accessible to everyone. We have ways to request reasonable accommodations during the interview process and help assist in what you need. If you need accommodations at any stage of the application or interview process, please let us know - we’re here to support you in any way we can.