Senior Backend Engineer

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.

We're looking for a Senior Backend Engineer to join our growing Product Engineering team. As a Backend Engineer, you'll play a pivotal role in helping to build the canonical tools and products to protect digital assets and preserve self-sovereignty in a post-quantum world.

This role is a full-time, fully remote position in Europe (GMT to GMT+2).

• Own and evolve a security-critical core library used by multiple applications and runtimes

• Design, implement, and maintain execution logic for blockchain transactions, signing flows, and protocol interactions

• Build and maintain robust abstractions over blockchain RPCs, transaction construction, and network interactions

• Enforce strict security boundaries around key handling, signing, and cryptographic operations

• Define and uphold API stability guarantees, versioning strategy, and backward-compatibility policies

• Contribute to internal security standards, documentation, and engineering best practices

• Strong proficiency in Rust & Typescript (ideally both)

• Experience building performant backend services, APIs and libraries at production scale

• Practical experience in Web3 development e.g. Ethereum JSON-RPC, Viem/Ethers, Contract ABIs, call encoding/decoding etc

• Good knowledge of CI/CD, service deployments, containerisation

• Strong security knowledge e.g. authentication/authorization, signature verification, secrets management, encryption (especially post-quantum)

• High competency with automated testing e.g. unit, integration and e2e testing

• Strong English communication

• Understanding of ERC-4337 smart wallet patterns e.g. EOA vs AA concepts, multisig basics, validation flows, bundlers/paymasters

• Experience with frontend development in React (or similar)

• Experience with iOS development or mobile development using React-Native

• Experience developing and maintaining protocols

• Experience with decentralised identity, DIDComm, encrypted messaging protocols

• Open-source contributions to Web3, Account Abstraction, Decentralised identity, Cryptography

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.