Blockchain Engineer

You'll own the systems that take a payment instruction and turn it into an immutable, on-chain record. You'll design and extend the integration layer between backend services and an institutional custody platform, ensuring transaction integrity from calldata construction through on-chain finality on a private ZKsync-based L2. You'll also work directly on the smart contract suite, maintaining upgrade safety, on-chain event integrity, and audit trails that satisfy compliance and evidentiary requirements of regulated bank partners.

Responsibilities

• Own the end-to-end transaction lifecycle: calldata construction, custody platform signing requests, nonce management, L2 submission, and finality confirmation
• Design and implement the signing pipeline architecture, including parallelization strategies, throughput management against custody platform rate limits, and async transaction submission patterns
• Build and maintain payment integrity controls: commitment hash verification at pipeline handoff points and co-signer policy evaluation to prevent tampering between transaction origination and on-chain execution
• Extend and harden Solidity smart contracts with a focus on upgrade safety, storage layout discipline, and role governance
• Develop and maintain a custody platform authorization policy integration and co-signer agent for custodian-owned transaction authorization
• Implement structured audit trails from transaction origination through on-chain execution, satisfying evidentiary requirements for bank partners under regulatory oversight
• Contribute to the design of an async transaction queue, enabling tiered SLAs and per-bank throughput quotas at scale
• Write high-coverage tests across backend services and smart contracts, maintaining the coverage threshold

Requirements

• 5+ years of backend software engineering experience, with at least 2 years working directly on EVM-compatible blockchain systems
• Strong proficiency in TypeScript; experience with Effect (effect.ts) or a comparable functional effect system is highly valued
• Deep familiarity with EVM transaction mechanics: ABI encoding, nonce management, gas estimation, revert handling, and event decoding
• Production experience with Solidity smart contract development, including upgradeable proxy patterns (UUPS preferred) and OpenZeppelin contract libraries
• Experience integrating with institutional custody or key management APIs (Fireblocks, Turnkey, Fordefi, or similar)
• Understanding of MPC signing infrastructure and the operational model of custodial signing pipelines
• Strong instincts around financial-grade reliability: idempotency, at-least-once delivery, crash recovery, and reconciliation in async transaction systems
• Comfortable operating with high autonomy in a small, fast-moving team where the architecture is still being defined

Benefits

• Remote-first work environment