FULLSTACK JS (NODEJS/REACTJS, SENIOR, HN)

As a Senior Fullstack Developer at Hola Tech., JSC, you design and lead the implementation of scalable backend services and frontend applications. You take technical ownership of one or more modules, from system design through rollout, and work on blockchain integration, microservices architecture, and high-concurrency systems.

What you'll do

• Design architecture and lead implementation of scalable backend services and frontend applications
• Take technical ownership of one or more modules: system design, service decomposition, API contracts, and rollout
• Design and implement blockchain integration flows: smart contract integration, wallet functionality, transaction signing and submission, on-chain event handling, and off-chain state synchronization
• Design microservices, distributed systems, and event-driven architecture; handle high-concurrency and large-scale transaction problems
• Optimize performance, scalability, and reliability; establish monitoring and alerting baselines
• Review code, establish coding standards, and mentor junior team members
• Work directly with product managers and designers to align scope and timeline; communicate technical details with international partners in English
• Investigate and resolve production incidents, performance bottlenecks, and complex system issues
• Make technical decisions and document them as Technical Design Documents

What you bring

• 4+ years of full-time fullstack development experience, with strong expertise in NodeJS/NestJS and practical experience with ReactJS
• Production blockchain experience: you have built or integrated smart contracts, wallets, on-chain data, or node infrastructure for real products, not just personal projects or hackathons
• Experience building and operating microservices, distributed systems, or high-concurrency platforms in production environments
• Hands-on experience with Docker, CI/CD, monitoring, and performance optimization
• Good English: able to conduct meetings, discuss technical matters, and write documentation with international partners
• Strong grasp of clean code, SOLID principles, scalable architecture, and system design
• Proficiency with REST APIs, asynchronous processing, caching, message queues, and event-driven architecture
• Understanding of EVM/Solidity or equivalent blockchain systems
• Experience with on-chain interaction libraries such as ethers.js, web3.js, viem, or equivalent
• Ability to handle gas optimization, nonce management, retries, and chain reorganizations
• Experience with PostgreSQL and Redis; familiarity with Neo4j or other NoSQL databases
• Cloud experience with GCP, AWS, Azure, or OVHcloud
• Strong understanding of application security, authentication/authorization, key management, and testing practices
• Proficient use of AI coding tools such as Claude or Codex in your development workflow
• Good problem-solving skills and autonomy in Agile/Scrum environments
• Experience with mentoring or technical ownership

What we offer

• Salary up to 40M VND gross
• 5-day work week, 7.5 hours per day, 9:00 AM to 6:00 PM (lunch break 12:00 PM to 1:30 PM)
• 100% salary during probation period
• Annual health check-ups
• Minimum 13 months of salary per year plus bonuses on holidays (Lunar New Year, International Labor Day, National Day, Mid-Autumn Festival, and others)
• Performance and project bonuses
• Salary increases evaluated twice per year
• Participation in company events and celebrations (birthdays, Women's Day, Men's Day, and others)
• Two company trips per year
• Company provides monitors and necessary equipment; employees provide their own laptops
• Training on technical skills, soft skills, and working methodologies
• Career development advice and mentoring
• Opportunities for advancement to leadership and management positions

About Hola Tech., JSC

Hola Tech., JSC is a technology company based in Hanoi. Learn more at https://hola.tech/