Principal / Senior Software Engineer

The Company FL105 is a privately held, early-stage company pioneering the use of artificial intelligence to transform human psychological fitness and wellbeing. We are creating a platform that empowers people to build a life they are proud of and fulfilled by. FL105 is backed by Flagship Pioneering, an innovation enterprise that conceives, creates, resources, and builds companies that invent breakthrough technologies that transform the world. Flagship has created over 100 groundbreaking companies since 2000, including Moderna. The Role We are seeking an experienced, creative, and talented Principal / Senior Software Engineer. The ideal candidate will have a strong background in software and product development, with the ability to lead projects and communicate effectively across teams and with ML researchers. Key Responsibilities In this role, you will: Lead the design and development of customer-facing features across the front-end and back-end application stack. Partner closely with product managers, designers, and researchers to translate customer needs and product strategy into well-designed, high-impact features. Own features throughout the full product development lifecycle, from discovery and technical design through implementation, release, measurement, and iteration. Manage the release process for new features, including rollout planning, feature flagging, monitoring, and coordination across engineering and product teams. Use product analytics, feature experiments, and customer feedback to evaluate feature performance and guide continued development. Design scalable system architecture for rapidly evolving, AI-enabled back-end components. Contribute to user interface and interaction design, bringing technical insight into product and design decisions. Improve application delivery practices by implementing continuous integration, continuous delivery, automated testing, and operational best practices. Leverage AWS cloud infrastructure to build scalable, relia