Senior Node.js Developer

⭐️ CoreStar is a dynamic technology company supporting partners in heavy-load industries with high-performance solutions. Our expert teams bring a startup-driven mindset, focusing on innovation, collaboration, and efficiency in every project. At CoreStar, you’ll have the opportunity to grow your skills, tackle exciting challenges, and directly contribute to impactful products.

Project:

High-load in-house platform handling multiple third-party integrations, data collection, and comprehensive reporting systems. The system processes large volumes of real-time data and requires high availability with performance optimization.

📌 Key Responsibilities:

• Develop scalable backend systems - design and implement high-load applications capable of handling massive traffic with optimal performance
• Build robust APIs and microservices - create RESTful services, GraphQL APIs, and real-time WebSocket connections for complex distributed systems
• Optimize application performance - identify bottlenecks, implement caching strategies, and ensure optimal resource utilization in production environments
• Design and implement third-party integrations - connect external APIs, payment systems, and various service providers while maintaining system reliability
• Develop from concept to production - participate in the full development lifecycle, from initial architecture design through deployment and monitoring

📌 AI-Assisted Development

• Deliver with agents as a normal way of working - break work down so that a meaningful part of it can be handed to agents, and use them daily rather than occasionally
• Contribute to shared AI tooling - write and improve reusable skills, commands and automation that the rest of the team uses, instead of keeping your workflow private
• Automate repetitive engineering work - identify what should not be done by hand any more and remove it

📌 Technical Excellence

• Ensure code quality and maintainability - write clean, well-documented code following best practices and design patterns
• Monitor and troubleshoot production systems - investigate complex issues, optimize database queries, and maintain system stability
• Collaborate with cross-functional teams - work closely with product managers, designers, and other developers to deliver high-quality solutions
• Stay current with technology trends - continuously learn and evaluate new tools, frameworks, and best practices in the Node.js ecosystem

📌 Requirements:

• 5+ years of professional software development experience with a strong focus on backend systems
• 4+ years of hands-on Node.js development in production environments with deep understanding of JavaScript runtime internals
• 3+ years of experience with high-load systems - building applications that serve large user bases with high availability requirements
• Proven track record of performance optimization - experience with scaling applications, database optimization, and system architecture

📌 Technical Skills

• Advanced JavaScript and TypeScript proficiency - ES6+, async/await, promises, and TypeScript for large-scale applications
• Node.js ecosystem mastery - Express.js, Fastify, or similar frameworks with deep understanding of event loop and performance optimization
• API development expertise - RESTful services, GraphQL implementation, WebSocket connections, and third-party API integrations
• Database optimization - MySQL, MongoDB, Redis / Valkey with advanced query optimization, indexing strategies, and schema design
• Message queuing and streaming - NATS or Apache Kafka for building distributed, event-driven architectures
• Monitoring and observability - Prometheus, Grafana, ELK stack for comprehensive system monitoring and debugging
• Containerization and orchestration - Docker for development and deployment, Kubernetes for production scaling
• Cloud platform proficiency - AWS or Azure services with experience in auto-scaling, load balancing, and distributed systems

📌 AI Engineering

• Hands-on experience with agentic development tools - Claude Code or equivalent, used as part of daily delivery
• Experience creating reusable AI tooling - skills, commands, agent workflows or MCP integrations that other people also use
• Verification discipline - treats model output as something to be checked before it is acted on

📌 Additional Qualifications

• Strong English communication skills - ability to participate in technical discussions and document complex systems
• Performance-focused mindset - deep understanding of scalability principles, caching strategies, and optimization techniques
• Problem-solving expertise - capacity to debug complex distributed systems and design elegant solutions for challenging technical problems
• AI-ready mindset - actively looks for work that can be moved from people to agents, and adapts how they work as the tooling changes

📌 Benefits:
🏝 24 working days of paid annual leave
🤝 6 days of paid sick leave
🖊 Official employment
📄 Medical insurance
☕️ Coffee zone with fruit & snacks available in the office
🥗 Corporate Lunch provided by the company
💪 Gym and sports classes
🙌 Healthy and friendly work atmosphere
📚 Greek and English language classes (partially covered)

Join us and be one of the Core Stars! ⭐