Senior Blockchain Engineer

The Cari Network is building a blockchain-based payment system powering real-time, 24/7 movement of digital money across the traditional finance and digital asset ecosystems. A pre-launch startup, we're building an entirely new category of financial infrastructure that brings cash on chain through tokenization while powering the full spectrum of payments for our network-banks, digital asset exchanges, and, most importantly, the customers they serve.

About the Role

You'll own the systems that take a payment instruction and turn it into an immutable, on-chain record—as the trusted technical decision-maker for that domain. That means designing and extending the integration layer between our backend services and our institutional custody platform, and being accountable for transaction integrity from calldata construction through on-chain finality on our private ZKsync-based L2.

You'll also own significant parts of our smart contract suite, maintaining upgrade safety, on-chain event integrity, and audit trails that satisfy the compliance and evidentiary requirements of regulated bank partners.

What You'll Do

• Own the end-to-end transaction lifecycle as a domain: calldata construction, custody platform signing requests, nonce management, L2 submission, and finality confirmation
• Design the signing pipeline architecture - parallelization strategies, throughput management against custody platform rate limits, and async transaction submission patterns - and write the RFCs other engineers build against
• Define what production-ready means for the signing pipeline: alerting thresholds, runbooks, and SLOs, and lead incident response and root-causing when it falls short
• 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 our Solidity smart contracts with a focus on upgrade safety, storage layout discipline, and role governance
• Develop and maintain the 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
• Drive the design of the async transaction queue, enabling tiered SLAs and per-bank throughput quotas at scale
• Mentor engineers earlier in their blockchain careers, and be the team's go-to for EVM transaction mechanics and custody integration questions
• Push back on scope or timeline with technical reasoning when a proposed change puts pipeline correctness at risk

Qualifications

• 5-7 years of backend software engineering experience, with at least 3 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
• 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 owning a domain independently and writing design docs that other engineers act on without you in the room
• Experience mentoring junior engineers

Nice to Haves

• Experience with ZKsync or ZK Stack-based chains -particularly developer-facing constraints like calldata handling, system contract interactions, and AA transaction formats
• Familiarity with Kafka or message-queue-backed async signing pipelines
• Prior work in fintech, payments, or any regulated financial infrastructure environment
• Experience building or operating blockchain event indexers or transaction monitors
• Foundry proficiency (forge test, forge fmt, Foundry Upgrades for storage layout validation)
• Experience mentoring junior engineers

What We Offer

• Competitive compensation: salary, bonus, and equity
• 401(k) with matching program
• Flexible vacation policy (PTO) and remote-first work environment