Rust Senior Engineer - layer

The Team

Founded in 2020, Synonym is preparing for the post‑Bitcoin economy by designing and developing an ecosystem of products and protocols that includes Pubky, Bitkit, Blocktank and now Atomicity. Synonym empowers individuals to take control and ownership of their digital lives. We are committed to the principles of digital autonomy, privacy, and open‑source technology.

Synonym is an entirely remote team working to bring new integrated products to open source protocols and cutting‑edge peer‑to‑peer technology.

We are seeking a Senior Rust Engineer with a strong payment layer background to join our team and contribute to the implementation of Atomicity, our open protocol for peer‑to‑peer mutual credit issuance, settlement, and routing of trusted payments.

Atomicity treats credit as a settlement method, alongside Bitcoin on‑chain and Lightning. Building it well requires deep familiarity with how real‑world payment layers actually behave: HTLCs and timelocks, channel states, fee mechanics, refund and recovery flows, atomic swaps. Whether your background is Lightning, on‑chain Bitcoin, or any other payment / L2 protocol, we want someone who has shipped payment code in production and knows where the sharp edges are.

This position is for an engineer who is comfortable thinking in terms of channels, states, timeouts, and adversarial counter parties, and who can translate that intuition into clean Rust code.

• Contract type: Full‑time
• Location: Remote only
• Salary: Based on experience, be prepared to communicate your requirements

• Settlement Design: Design and implement the settlement layer of Atomicity, including credit channels, state transitions, timeouts, refund paths, and integration with Bitcoin as underlying settlement rails.
• Channel & State Engineering: Build robust state machines for credit channels (open, update, dispute, close), with attention to failure modes, partial states, and recovery.
• Payment Coordination: Work with the Paykit team to integrate Atomicity as a payment / settlement method alongside on‑chain Bitcoin, including proof generation and verification flows.
• Integration: Coordinate with the Blocktank, Bitkit, and Lightning teams (LDK) to make sure Atomicity composes cleanly with existing Synonym payment infrastructure.
• Reliability & Recovery: Treat money and credit as critical. Design clear failure modes, robust retries, idempotent flows, and recovery procedures for stuck or partial payments.
• Innovation: Stay informed about payment protocol research (PTLCs, atomic swaps, payment routing) and bring relevant ideas back into Atomicity.

• Expertise in Rust: Proven experience building production‑grade systems in Rust, ideally including networked or financial components.
• Payment Layer
  
  Experience:
  
  Hands‑on experience building, integrating, or operating a payment protocol in production. This can be Lightning, atomic swaps, or another L2 / payment system.
• State Machines & Concurrency: Strong intuition for protocol state machines, async runtimes, idempotency, and edge cases (timeouts, retries, partial failures).
• Money‑Grade Engineering: Deep care for correctness, auditability, and recoverability when value is at stake.
• Data & APIs: Familiarity with database management, persistent state, and RPC / API design for payment flows.
• Collaboration: Strong communication skills and the ability to work effectively in a fully remote team setting.
• AI‑Assisted Engineering: Comfortable using LLM‑based coding tools in daily workflow. Ability to critically evaluate AI‑generated code for correctness, security, and performance.

• Lightning Network: Practical experience with LDK, LND, CLN, or Eclair, and a working understanding of BOLT specs, HTLCs, and routing.
• Atomic Swaps & HTLC Patterns: Prior work on submarine swaps, reverse swaps, Boltz‑like services, or cross‑chain atomic swaps.
• Other Payment Layers: Experience with other L2s, payment channel networks, or payment‑oriented blockchains (the more battle scars, the better).
• Mutual Credit: Familiarity with ecash, Offset, Trustlines, or other mutual credit / IOU systems.
• Decentralized / P2P Systems: Exposure to peer‑to‑peer architectures, DHTs, gossip protocols, libp2p.
• Cryptography: Working knowledge of signatures, hash chains, and HTLC / PTLC mechanics.

• Impactful Work
  :
  Play a key role in shaping next‑generation technologies that empower individuals and communities.
• Growth & Ownership
  :
  Enjoy the flexibility to define your role, innovate, and lead initiatives.
• Cutting‑Edge Environment
  :
  Collaborate with a forward‑thinking, decentralized team working on Bitcoin and peer‑to‑peer ecosystems.
• Remote Culture
  :
  Work from anywhere with flexible hours. We prioritize productivity and well‑being.
• Time Off
  : 28 vacation days per year.