Job title: Software Engineer, Cloud Infrastructure at Cosine Location: London; full in-office working as default

Start date: ASAP

Reports to: CTO

Compensation: £60 - 90k + Equity

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Cosine at a glance At Cosine, we’re building autonomous AI engineers that plan, write, and ship code inside real development workflows.

Cosine is designed for on-premise and virtual private cloud (VPC) deployments, including fully air-gapped environments. We build our agent tooling entirely in-house and post-train open-source models to deliver reliable, enterprise-grade coding performance in security-critical settings.

In 2024, Cosine achieved a 72% score on OpenAI’s SWE-Lancer benchmark, placing us among the strongest real-world software-engineering AI systems evaluated.

YC-backed and well-funded, Cosine was founded by experienced operators focused on building dependable, production-grade AI.

This role is based in our Hoxton office, five days a week, because close collaboration, fast feedback, and shared context matter for the problems we’re solving. ___________________________________________________________________________

The role As an Enterprise Account Executive for Defence, you will own and close complex enterprise deals across defence primes, government agencies, and national security organisations. You will navigate highly regulated procurement environments and work closely with senior technical, security, and programme stakeholders to turn pilots into long-term production deployments.

This role is ideal for someone who has successfully hunted and closed new logo enterprise deals within defence or government, particularly selling developer tooling, infrastructure, security, or platform technologies into mission-critical engineering teams.

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About The Role An Applications Engineer at Cosine works across research, engineering, product, and design to deliver advanced AI capabilities to consumers and enterprises.

You will be responsible for the core infrastructure powering Cosine’s products, including our Kubernetes environments, deployment pipelines, networking stack, cloud abstractions, and foundational platform services.

We build systems that enable rapid product iteration while maintaining operational excellence, with a strong emphasis on enterprise-grade reliability. Our work includes supporting large‑scale deployments for regulated industries, delivering hardened on‑premises installations, and ensuring secure, isolated environments for customers with stringent operational or compliance requirements

The Cloud Infrastructure engineer develops and maintains the infrastructure abstractions that allow Cosine to ship products reliably, securely, and at scale.

In This Role, You Will

• Design and build development and production platforms that power Cosine products, enabling reliability and security at scale.
• Ensure our infrastructure can scale to the next order of magnitude.
• Contribute to a culture that values diversity, rigorous thinking, and open, direct communication.
• Participate in the on-call rotation to ensure reliability of the systems you build, responding to critical incidents when necessary.

You Might Thrive In This Role If You

• Have 5+ years of experience developing or operating core infrastructure.
• Have experience running large-scale orchestration systems such as Kubernetes.
• Have built abstractions and tooling on top of major cloud platforms.
• Take pride in building scalable, reliable, and secure systems.
• Are comfortable working in a fast-moving environment with evolving priorities.

About Cosine Cosine builds infrastructure, tooling, and products that make advanced AI systems practical, powerful, and widely accessible. This includes enterprise‑grade and fully on‑premises deployments designed for customers requiring strict isolation, compliance, or custom security postures. We support bespoke model hosting, fine‑tuned and custom models tailored to domain‑specific workflows, and deep integration with customer infrastructure. Cosine also offers a collaborative coding agent platform built for teams and enterprises, enabling secure, auditable AI‑assisted software development across complex codebases.

We create and deploy AI with a focus on performance, robustness, and real‑world impact. Achieving this requires a team that reflects a wide range of perspectives, backgrounds, and experiences.

Cosine is an equal opportunity employer. We value diverse backgrounds, perspectives, and ways of thinking, and we’re committed to creating an inclusive and respectful workplace.

We encourage applications from anyone who meets the role requirements, even if you don’t meet every single qualification. If you need reasonable adjustments at any stage of the hiring process, we’re happy to discuss them.

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Compensation, Benefits & Ways Of Working We’re an in-office team, five days a week, by design. We believe the work we’re doing benefits from being together, collaborating closely, and building shared context.

What You Can Expect

• Competitive salary, benchmarked to the market
• Equity / share options, so you share in the upside you help create
• 30 days’ holiday + bank holidays
• Genuine 9–5 working hours — we don’t expect late nights or weekend work
• Work hard in the office, collaborate closely, and switch off properly
• Dog-friendly office — bring your dog to work
• Daily lunch provided
• Monthly team breakfasts

We care about focus, sustainability, and doing great work — not performative overwork. We value people who show up, contribute thoughtfully, collaborate well with their colleagues, and then go home.

This role won’t suit everyone. But if you want structure, clarity, strong collaboration, and a team that takes both the work and work-life balance seriously, it’s a great place to be.