Salary range: B2B - 38-42 E/h + VAT 💰Ciklum is looking for a Senior Fullstack Developer to join our team full-time in Poland.We are a custom product engineering company that supports both multinational organizations and scaling startups to solve their most complex business challenges. With a global team of over 4,000 highly skilled developers, consultants, analysts and product owners, we engineer technology that redefines industries and shapes the way people live. About the role:As a Senior Fullstack Developer, you will drive the design and development of our core APIs and on-premise cloud infrastructure, with a relentless focus on security, performance, and scalability. Your initial focus will be on integration and enhancement of a critical Passenger Information System (PIS) with train systems. Responsibilities: Drive technical decisions and promote best practices in API design, microservices, testing, and deployment Develop scalable backend services and clean, reusable frontend components Optimize services for maximum speed and low latency, and proactively identify and resolve performance bottlenecks Mentor and guide team members, fostering a culture of technical excellence, security consciousness, and continuous improvement Own and enhance our CI/CD pipelines to ensure efficient, automated, and reliable software delivery Collaborate closely with Product and Design to translate business requirements into robust and secure technical solutions Requirements: 5+ years of professional experience in fullstack web development Proven experience in designing, building, and maintaining secure, distributed systems Strong, hands-on expertise with JS, TypeScript, Node.js, and Angular Deep understanding of API security principles and best practices (e.g., OWASP Top 10, rate limiting, input validation) Proficient with CI/CD practices and tools (e.g., Jenkins, GitLab CI, GitHub Actions) Hands-on experience with containerization using Docker and an understanding of orchestration (e.g., ECS, Kubernetes) Skilled in working with both NoSQL (e.g., MongoDB, DynamoDB) and relational databases (e.g., PostgreSQL), including performance tuning Experience with monitoring, logging, and observability tools (e.g., CloudWatch, Datadog, Grafana) Strong problem-solving skills and a passion for code quality and technical excellence Upper-intermediate or higher level of spoken and written English Desirable: Experience with Next.js, CSS Modules, SASS, or Styled Components Familiarity with event-driven architectures and microservices Familiarity with Infrastructure as Code (e.g., CloudFormation, Terraform) Working experience with .Net or Python Personal skills: Accountability: You take ownership and follow through on your responsibilities Drive: You're proactive and results-oriented, always seeking better ways to solve problems Self-development: You stay curious, seek feedback, and aim for continuous improvement Effective communication: You communicate your ideas clearly and collaborate effectively in a team Mentoring: You're open to helping less experienced team members and sharing knowledge  What`s in it for you? Strong community: Work alongside top professionals in a friendly, open-door environment Growth focus: Take on large-scale projects with a global impact and expand your expertise Tailored learning: Boost your skills with internal events (meetups, conferences, workshops), Udemy access, language courses, and company-paid certifications Endless opportunities: Explore diverse domains through internal mobility, finding the best fit to gain hands-on experience with cutting-edge technologies Flexibility: Enjoy flexibility – full remote working possibilities Care: We’ve got you covered with company-paid medical insurance, mental health support, and financial & legal consultations About us:At Ciklum, we are always exploring innovations, empowering each other to achieve more, and engineering solutions that matter. With us, you’ll work with cutting-edge technologies, contribute to impactful projects, and be part of a One Team culture that values collaboration and progress.With delivery centers in Wrocław and Gdańsk, our 300+ professionals in Poland drive forward-thinking solutions for global clients. Join a community where collaboration sparks innovation—and your impact reaches millions.Want to learn more about us? Follow us on Instagram, Facebook, LinkedIn.Explore, empower, engineer with Ciklum!Interested already? We would love to get to know you! Submit your application. We can’t wait to see you at Ciklum.