Blockchain Engineer

# Blockchain Engineer **Location:** Remote — United States **Employment Type:** Full-time **Experience Level:** Mid-Level ## About the Company Our client is building blockchain-based payment infrastructure that enables the real-time, 24/7 movement of digital money across traditional financial institutions and the digital asset ecosystem. As a pre-launch startup, Cari is creating infrastructure that brings cash on-chain through tokenization and supports payments for banks, digital asset exchanges, and their customers. ## About the Role We’re looking for a Blockchain Engineer to help build and extend the systems that transform payment instructions into immutable on-chain records. You’ll contribute to an established transaction pipeline architecture, working alongside senior engineers who own its overall design. Your work will span backend services, institutional custody integrations, EVM transaction processing, and Solidity smart contracts deployed on a private ZKsync-based Layer 2 network. This is a hands-on implementation role for an engineer with a strong backend foundation and practical experience with EVM-compatible blockchain systems. You should be comfortable extending established patterns, asking for guidance when needed, and gradually taking ownership of increasingly complex features. ## What You’ll Do - Implement components across the on-chain transaction lifecycle, including calldata construction, signing requests, nonce management, L2 submission, and finality confirmation. - Build new features within the institutional custody signing pipeline, including submission paths, asynchronous transaction handling, and throughput management against custody-platform rate limits. - Implement payment integrity controls, such as commitment-hash verification and co-signer policy evaluation. - Extend existing Solidity smart contracts while following established upgrade-safety, storage-layout, and role-based governance conventions. - Contribute to custody authorization policy integrations and co-signer agents used to approve custodian-owned transactions. - Build structured audit-trail logging that follows transactions from origination through on-chain execution. - Help maintain an asynchronous transaction queue with tiered SLAs and per-bank throughput quotas. - Write comprehensive automated tests for backend services and smart contracts. - Participate in an on-call rotation, independently resolving known issue patterns and escalating novel failure modes when appropriate. - Collaborate closely with senior engineers to understand and extend the platform’s existing architectural patterns. ## Required Qualifications - 3–5 years of professional backend software engineering experience. - 1–2 years of hands-on experience working with EVM-compatible blockchain systems. - Strong proficiency in TypeScript. - Practical understanding of EVM transaction mechanics, including: - ABI encoding - Nonce management - Gas estimation - Revert handling - Event decoding - Production experience developing or maintaining Solidity smart contracts. - Familiarity with upgradeable proxy patterns, particularly UUPS, and OpenZeppelin contract libraries. - Understanding of asynchronous system concepts such as idempotency, at-least-once delivery, retries, and crash recovery. - Strong automated testing practices across backend and smart contract codebases. - Ability to work effectively within an established architecture and seek guidance when encountering unfamiliar patterns. - Availability to work remotely within the United States. ## Nice to Have - Experience with Effect (`effect.ts`) or another functional effect system. - Experience integrating institutional custody, signing, or key-management APIs. - Familiarity with ZKsync or ZK Stack-based networks. - Understanding of ZKsync-specific development considerations, including calldata handling, system contract interactions, and account-abstraction transaction formats. - Experience with Kafka or other message-queue-backed asynchronous pipelines. - Previous work in fintech, payments, banking, or regulated financial infrastructure. - Proficiency with Foundry, including `forge test` and `forge fmt`. ## What Success Looks Like - You can independently implement well-defined features within the existing transaction pipeline. - You produce reliable, well-tested code across TypeScript services and Solidity contracts. - You understand how backend transaction processing connects to custody authorization and on-chain execution. - You follow established security, upgradeability, governance, and auditability patterns. - Over time, you take ownership of larger components while collaborating effectively with the senior engineers responsible for the platform architecture. ## What We Offer - Competitive compensation. - Remote-first working environment. - The opportunity to help build a new category of financial infrastructure. - Close collaboration with an experienced founding and engineering team. - Meaningful influence over the product at an early stage.