Senior Core Systems Engineer

About

Dfns is the leading Wallets-as-a-Service (WaaS) platform, helping fintechs, institutions, and enterprises simplify digital asset management and securely onboard users onchain.

Its API-first wallet platform unifies transaction management, workflow governance, key deployment, and third-party integrations into one secure operating system for blockchains. Built on advanced security and cryptography, Dfns is trusted by over 200 financial institutions and applications—including ABN AMRO, Broadridge, Fidelity, Zodia Custody, Banca Sella, Stripe, Moonpay, Circle, IBM, Deblock, and Gemini—and secures over $3 billion in monthly transactions.

Founded in 2020, Dfns has raised $30 million from global investors such as White Star Capital, Motive Partners, Bpifrance, Coinbase, Wintermute, and Susquehanna. Originally incubated by Techstars and Station F in Paris, Dfns now operates globally with teams across the US, Europe, the Middle East, and Asia.

Job Description

Join a stellar team of leaders and experts in blockchain technology, cryptography, infrastructure, and security to build the backbone of blockchain wallet infrastructure for the next financial era. We’re hiring a Core Systems Engineer to design, build and scale the systems at the heart of our platform: MPC, HSMs, TEEs, and the middleware that ties them together. You’ll work deep in the stack, building reliable distributed services and integrating them with cloud, hardware, and blockchain environments. This is a low-level, high-impact role where performance, security, and correctness are non-negotiable. You’ll design protocols, optimize databases, and harden workflows that power financial applications at scale. You’ll collaborate across product, research, and security to turn advanced cryptography into Rust-based, production-ready infrastructure that is fast, resilient, and trusted.

Preferred Experience

Responsibilities

  • Design, implement, and operate MPC signers, HSMs, and TEEs (e.g. AWS Nitro).

  • Build low-level services and middleware in Rust and other systems languages.

  • Architect distributed databases and stateful services for performance and reliability.

  • Develop secure APIs and networking between core systems and high-level services.

  • Optimize resource usage, latency, and throughput across critical workflows.

  • Collaborate with cryptography, infra, and product to bring new protocols into production.

  • Document core systems, share knowledge, and support client and partner discussions.

Requirements

  • 8+ years of systems engineering experience with focus on security, infra, or backend.

  • Deep expertise in Rust, with strong low-level systems programming skills.

  • Proven experience building distributed systems, consensus mechanisms, or networks.

  • Hands-on experience with HSMs, MPC, TEEs, and cryptographic key management.

  • Strong knowledge of SQL and NoSQL databases in high-availability environments.

  • Familiarity with secure networking, applied cryptography, and defense-in-depth models.

  • Skilled in observability, debugging, and optimizing performance at scale.

  • Clear communicator, able to translate complex systems into practical solutions.

Recruitment Process

Process

  • Intro call with Co-CEO (30 min).

  • Personality and cognitive tests (45 min)

  • Coding test in a language of your choice.

  • Focus interviews with the hiring panel (180 min).

    • Code review
    • Architecture review
    • Security fundamentals
    • Culture check fit

  • Final interview with CTO (30 min).

  • Reference calls and background checks.

Terms

  • Title: Senior Core Systems Engineer.

  • Salary: $180,000-260,000 per year (full-time).

  • Equity: 100-200 stock options vested over 4 years.

  • Benefits: Healthcare, 401K, and travel expenses.

  • Location: US or EU (remote-first, office optional).

  • Equipment: MacBook Pro + essentials.

Additional Information

  • Contract Type: Full-Time
  • Location: Paris, New York
  • Experience: > 7 years
  • Possible full remote
  • Salary: between 180000$ and 260000$ / year
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