Senior Software Engineer - Login Platform in London

The Login Platform group covers all aspects of user authentication and experience across Terminal and Enterprise (non-Terminal) workflows. This includes teams that manage the company’s Single Sign-On (SSO), Multi-Factor Authentication, user login experience, and the sessions platform used to propagate authentication and authorization context throughout the company ecosystem. Sessions are the backbone of authorization decisions across the company. They are created from entry points including the Terminal, Mobile, Enterprise applications, Web, and more. These sessions need to include the correct entitlements, customer data, and security context so that application teams can make the accurate entitlement decisions.

We’re evolving our session and authorization infrastructure to support AI agents, MCP-based integrations, and machine-to-machine workflows across the company systems. We are hiring Senior Software Engineers for two closely related teams in London focused on session infrastructure and session lifecycle management.

Where we sit: We’re part of Login Platform within the Platform Security organization, operating deep in the infrastructure stack. Our teams own the framework that orchestrates sessions enrichment flows, while data-owning teams provide and manage the underlying datasets. Almost every business unit at the company depends on our platform to make authorization and access-control decisions. Our software is critical to maintaining the company’s reliability, compliance, and continued growth. Because of our position in the stack, we enforce security not only for others, but for ourselves as well.

What you’ll do: As a Senior Software Engineer, you’ll play a key role in shaping and scaling the infrastructure that powers session creation, enrichment and authorization across the company. You will:

• Design, build, and optimize low-latency, multi-threaded backend systems that handle session and authorization data at scale.
• Collaborate with multiple Engineering and Product teams to deliver a reliable and secure login experience.
• Contribute to architectural decisions and long-term technical strategy for the Login Platform.
• Improve tooling, observability, scalability, and performance across critical infrastructure services.
• Explore and champion new ideas to evolve our systems responsibly over time.

Engineers on the team are involved throughout the software lifecycle, including design, deployment, observability, incident response, and long-term platform evolution.

Our technologies: We work primarily in C++ and some Python, running mostly on Linux, with continued support for Solaris clients until full migration is complete. Because we sit deep in the infrastructure stack, you’ll often need to balance innovation with compatibility, designing modern, robust solutions that coexist with legacy systems.

You’ll need to have:

• Strong software engineering experience in C++, ideally building backend, infrastructure, platform, or systems-level software.
• Experience designing, building, or operating distributed backend systems, ideally in high-availability, low-latency, or infrastructure-heavy environments.
• Strong experience designing and building multi-threaded or concurrent applications.
• Experience owning software across the full lifecycle, including design, implementation, testing, deployment, observability, incident response, and long-term evolution.
• Ability to make pragmatic system design decisions across performance, scalability, reliability, maintainability, and compatibility constraints.
• An eagerness to understand a large, non-trivial stack and propose incremental improvements without compromising reliability or security.
• Strong communication and collaboration skills, with the ability to work effectively across Engineering, Product and platform-dependent teams.
• A Degree in Computer Science, Engineering, Mathematics, similar field of study or equivalent work experience.

We’d love to see:

• Background in authentication, authorization, identity, access control, entitlement systems, SSO, MFA, session management, or security-sensitive infrastructure.
• Familiarity with systems that propagate authentication, authorization, entitlement, or security context across distributed services.
• A track record of building low-latency, reliable backend or infrastructure services.
• Hands-on involvement in improving observability, scalability, performance, reliability, or operational tooling for production systems.
• Exposure to platform teams that support multiple internal product or application teams.
• Experience working across multiple business units or products, with an understanding of their operational and integration challenges.

If indicated, please note that years of experience are a guide; we will consider applications from all candidates who can demonstrate the skills necessary for the role.

Accommodations: The company provides reasonable adjustment/accommodation to individuals with disabilities. Please tell us if you require a reasonable adjustment/accommodation to apply for a job. Examples of reasonable adjustment/accommodation include but are not limited to making a change to the application process or work procedures, providing documents in an alternate format or using specialized equipment.

Equal Opportunity: The company is an equal opportunity employer and prohibits discrimination in employment. It is the company’s policy to provide equal opportunity and access for all persons, and the Company is committed to attracting, retaining, developing, and promoting the most qualified individuals without regard to age, ancestry, color, gender identity or expression, genetic predisposition or carrier status, marital status, national or ethnic origin, race, religion or belief, sex, sexual orientation, self-identified or perceived sex, sexual and other reproductive health decisions, parental or caring status, physical or mental disability, pregnancy, childbirth or related medical conditions, or parental leave, protected veteran status, status as a victim of domestic violence, or any other classification protected by applicable law (each, a “Protected Characteristic”). The company prohibits treating applicants or employees less favorably in connection with the terms and conditions of employment, in all phases of the employment process, because of one or more Protected Characteristics.