Full-Stack API Developer – Merchant Integration

Hyphenconnect

Vietnam (APAC) Remote permanent

Posted: August 31, 2025

Job Description

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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