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! ⭐