Senior Backend Engineer

Job description

ABOUT PROJECT ELEVEN Project Eleven is an applied lab of builders and technologists working at the intersection of quantum computing and cryptography. We build impactful solutions that push the digital-asset ecosystem to a more secure future. Our focus is post-quantum migration: upgrading wallets, identity, and settlement rails to quantum-safe primitives without breaking UX, composability, and developer workflows. Our mission is to future-proof digital assets and preserve self-sovereignty in a post-quantum world. We do that by building the canonical tooling and products teams can adopt: crypto-agile infrastructure, reference implementations, and integrations that fit real constraints like latency, cost, compatibility, key rotation, and recovery. We work with leading ecosystems to make this migration real through products we build, audits, testnets, and cutting edge research. The vision we are have is clear: a proven upgrade path, production-ready tooling and users retaining control of their assets and identity, before CRQC exists. THE ROLE We're looking for a Senior Backend Engineer to join our growing Product Engineering team. You'll play a pivotal role in building the canonical infrastructure that protects institutional digital-asset operations in a post-quantum world. This role is a full-time, fully remote position in Europe (GMT to GMT+2). WHAT YOU'LL BE RESPONSIBLE FOR - Owning and evolving security-critical backend services at the core of our institutional product - Designing and implementing systems with strict correctness, durability, and auditability guarantees - Enforcing strict security boundaries around sensitive operations and data - Defining and upholding API stability, versioning, and backward-compatibility policies - Contributing to internal security standards, threat modeling, and engineering best practices - Partnering with our cryptography and research engineers to bring novel primitives into production systems WHAT YOU BRING - Strong proficiency in Rust and TypeScript (ideally both) - Experience building performant backend services, APIs, and libraries at production scale - Experience designing systems with strong security, durability, or correctness requirements e.g. financial systems, key management, identity, custody, or other regulated infrastructure - Solid applied cryptography fundamentals: signing, encryption, secrets management, key handling - Good knowledge of CI/CD, service deployments, and containerisation - High competency with automated testing (unit, integration, and e2e) - Strong English communication WHAT WE'D LOVE TO SEE - Experience building or operating institutional infrastructure: custody platforms, HSM-backed systems, KMS, or similar high-assurance systems - Familiarity with threshold signing, MPC, or HSM integration patterns - Exposure to compliance frameworks (SOC 2, ISO 27001) and audit-friendly system design - Experience with post-quantum cryptography or the operational implications of migrating cryptographic primitives - Experience developing and maintaining long-lived libraries or protocols with strong backward-compatibility requirements - Open-source contributions to cryptography, security, or related infrastructure EQUAL OPPORTUNITY We are committed to equal employment opportunity and believe that diverse teams build better products. All qualified applicants will receive consideration without regard to any protected characteristic under applicable law.