As a Senior Security Engineer, you will be the primary security contact for large engineering projects, collaborating throughout the development lifecycle. You will conduct security reviews, develop threat models, and use these insights to establish best practices. You will contribute to defining, automating, and advocating for platform-wide security enhancements. Your responsibilities involve identifying areas for improvement, building relationships with teams to promote security, staying up-to-date with the latest security technologies, and communicating security recommendations effectively. You will also use data to optimize security review efficiency. This role involves making security decisions that affect millions of users.