Full-Stack API Developer – Merchant Integration

Published: 2025-09-01
Hyphen Connect Limited

Nexus of Web3 Talents. Your Web3 talent acquisition partner and beyond. Hyphen Connect, versatile yet impactful, serves as the fundamental building block within the complex Web3 ecosystem. We are the nexus of connection and growth, merging varied elements to create meaningful paths in the digital realm. As the pivotal link to top Web3 opportunities in infrastructure, DeFi, NFTs, gaming, and ...

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Job details

Vietnam, South-Eastern Asia (country)
Remote
Full-time

Categories

React
Vue.js
API
Node.js
Python
Back-end
Front-end
Developer
Full-stack
Tech lead
Network
Solidity
Web3
Crypto
Blockchain
Smart contract

Job Summary

We are hiring for an innovative crypto wallet and payment network startup who are looking for a Full-Stack API Developer to build and maintain merchant integration APIs, client portals, and SDKs for our crypto wallet app’s merchant payment system. You will develop backend services to support crypto-only payments via QR/NFC and POS, contributing to the January 2026 rollout. This remote role requires expertise in API development, merchant systems, and blockchain technology.

Responsibilities

  • Design and develop merchant-facing APIs and SDKs to enable crypto payments via wallet app.
  • Build and maintain merchant, admin, and customer portals for transaction management and reporting.
  • Integrate backend services with smart contract-based payment systems for secure transactions.
  • Collaborate with the Tech Lead and Integration Engineer to align APIs with merchant requirements.
  • Ensure scalability, security, and performance of APIs for online and physical POS environments.
  • Document APIs and SDKs for external developers and internal teams.

Qualifications

  • 5+ years of experience in full-stack development, with a focus on API and SDK development.
  • Proven experience building merchant or client portals for payment systems (e.g., fintech, e-commerce).
  • Strong proficiency in backend technologies (e.g., Node.js, Python, Go) and frontend frameworks (e.g., React, Vue.js).
  • Familiarity with blockchain technology and crypto wallets (e.g., Solidity, Web3.js, Ethers.js).
  • Experience with RESTful APIs and integration with payment gateways or POS systems.
  • Ability to work remotely and align with Hong Kong/Singapore time zones.
  • Bachelor’s degree in Computer Science, Engineering, or a related field (or equivalent experience).

Preferred Skills

  • Experience with crypto payment gateways (e.g., Coinbase Commerce, BVNK) and QR/NFC systems.
  • Knowledge of smart contract development and security (e.g., Hardhat, Foundry).
  • Familiarity with POS hardware integration for in-store payments.
  • Strong documentation skills for developer-facing APIs and SDKs.
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