Senior Backend Engineer

Project Eleven; United Kingdom; On-site; GBP 90,000 - 130,000; Full time

Job summary

A leading technology company is seeking a Senior Backend Engineer to join their Product Engineering team. This fully remote role focuses on developing secure tools for digital assets in a post-quantum world. Key responsibilities include evolving critical core libraries, designing blockchain transaction logic, and ensuring security in cryptographic operations. Ideal candidates should have strong Rust and Typescript skills, experience in Web3 development, and proficiency in automated testing. Join a diverse team committed to equal opportunity.

Qualifications

• Strong proficiency in Rust and Typescript.
• Experience building backend services at production scale.
• Practical experience in Web3 development and blockchain protocols.
• Knowledge of CI/CD and containers.
• Strong security expertise, especially in post-quantum contexts.
• Competency in automated testing.
• Strong English communication

Responsibilities

• Own and evolve a security-critical core library.
• Design and maintain blockchain transaction logic.
• Enforce security around cryptographic operations.
• Define API stability guarantees and versioning strategy.
• Contribute to documentation and engineering standards.
• Contribute to internal security standards, documentation, and engineering best practices

Skills

Rust

Typescript

Backend services

Web3 development

CI/CD

Security knowledge

Automated testing

English communication

Tools

Ethereum JSON‑RPC

Viem

Ethers

Contract ABIs

Call encoding/decoding

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. 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).

What you’ll be responsible for

• 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

What you bring

• 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

What we’d love to see

• 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

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.