Senior Backend Engineer (Blockchain Integrations & Wallet Infrastructure)

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Reap is seeking a Senior Backend Engineer to own the core multi-chain backend that powers stablecoin payments, wallet infrastructure, and card services. The ideal candidate brings 6+ years in backend development, with 2+ years shipping production Web3/Crypto, and is fluent in TypeScript/Node.js. You will design scalable AWS-based services, integrate with EVMs, Solana, and TRON, and lead gas abstraction and account abstraction patterns including ERC-4337. You’ll own API design, on-chain monitoring, incident response, and continuous improvement while collaborating closely with product, designers, and smart-contract engineers. To apply, highlight live mainnet projects, multi-chain experience, and evidence of gasless architectures, include relevant links, tailor your resume, and show ownership. After submitting, check your inbox for a confirmation email and adjust spam settings if needed.

About Reap

Reap is a global financial technology company headquartered in Hong Kong with employees across multiple countries. We enable financial connectivity and access for businesses worldwide by combining traditional finance with stablecoins for efficient money movement.

Through our stablecoin-powered corporate cards, payments, and expense management tools, we streamline financial operations and help businesses scale. Our APIs enable businesses to integrate stablecoin-enabled finance into their own products and services—from issuing Visa cards to facilitating cross-border payments.

Backed by leading investors including Index Ventures and HashKey Capital, Reap is building the future of borderless, stablecoin-enabled finance.

The Role

We’re looking for a Senior Backend Engineer who’s fluent in TypeScript/Node.js and excited to build production-grade systems that interact with live blockchains.

You’ll lead the buildout of the core backend and infrastructure behind our multi-chain platform—powering stablecoin-backed payments, wallet infrastructure, and card-related services for global businesses.

This role blends hands-on backend engineering with Web3-native systems work: integrating across EVM chains, Solana, and TRON, building gas abstraction / relayer infrastructure (including account abstraction patterns), and partnering closely with product and other engineers to ship end-to-end.

If you love owning complex systems—from API design and reliability to on-chain monitoring, incident response, and continuous improvement—this role is for you.

What You’ll Do

• Core Platform Design: Design, develop, and deploy scalable applications in our AWS environment, ensuring they meet business requirements and adhere to high-quality standards.

• Multi-Chain Integration: Architect and maintain robust integrations with multiple blockchains, specifically EVM-compatible chains (Ethereum, Base, Polygon), Solana, and TRON.

• Gas Abstraction & Relayer Infrastructure: Build and manage infrastructure to support sponsored (gasless) transactions. Implement Account Abstraction (ERC-4337 / EIP-7702) patterns to enable seamless user onboarding and fee subsidization across all supported chains.

• Wallet Infrastructure & Security: Lead the integration with enterprise-grade Wallet-as-a-Service (WaaS) and custody providers. Orchestrate programmable signing flows, and ensure secure implementation of embedded wallets.

• Collaboration: Work closely with cross-functional teams—including product managers, designers, and smart contract engineers—to ensure seamless product development from concept to deployment.

• Observability & On-Chain Monitoring: Build functional monitors and alerts for both off-chain services (AWS) and on-chain events (monitor pending tx pools, gas price spikes, and reorganization events). Investigate production incidents and apply learnings to code.

• Continuous Learning: Stay updated with the latest industry trends (e.g., L2 scaling solutions, new EIPs) to ensure our tech stack remains modern and competitive.

What We’re Looking For

Experience:

• Minimum of 6 years in backend development, with at least 2+ years dedicated to production-grade Web3/Crypto engineering.

• Proven track record of shipping products that interact with live mainnets (not just testnets).

Technical Proficiency (Web2):

• Strong knowledge in scalable software application design, API design (REST/GraphQL), and microservices architecture.

• Proficiency with Node.js, TypeScript or NestJS.

• Deep understanding of relational databases (PostgreSQL, MySQL) and ORM frameworks.

Technical Proficiency (Crypto Native):

• Chain Interaction: Deep familiarity with JSON-RPC standards and client libraries (e.g., viem, ethers.js for EVM; @solana/web3.js for Solana).

• Transaction Management: Expertise in handling nonces, gas estimation, transaction replacements, and re-org handling in a high-throughput multichain environment.

• Embedded Wallets & Custody: Experience integrating programmable MPC (Multi-Party Computation) wallets or embedded wallet solutions. Understanding of policy engines (allowlists, spending limits) and programmatic key signing.

• Gasless Architecture: Solid understanding of relayers, bundlers, and paymasters. Experience implementing architecture that abstracts gas fees away from the end user.

Bonus Points:

• Experience with Payments or Credit Card processing integrations.

• AWS Certified Solutions Architect or Developer.

• Smart Contract development experience (Solidity or Rust) to better understand the upstream logic.

Why Join Us

• Full Ownership: You’ll own the backend and on-chain integration architecture end-to-end—APIs, chain adapters, relayer/AA components, and the operational tooling to run it in production.

• Lean & Fast Team: No bureaucracy - direct alignment with founding engineers and product.

• High‑Impact Engineering: Your work directly powers global B2B payments and credit infrastructure.

• Fully Remote: Work flexibly from anywhere across Europe or Asia time zones.

• Cross‑Domain Opportunity: Operate at the intersection of fintech, cloud engineering, and Web3 innovation.

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