Full Stack Developer with React and C#, Web Platform

🏢 Summary: Long-term opportunity for a Middle/Senior Full Stack Developer to design, develop, and optimize a live educational platform using Node.js and React.js. The role covers both frontend and backend development, system architecture, integrations, and DevOps within a mature product continuously enhanced for performance and security. 🗂️ Requirements: 4+ years of professional software development experience, 4+ years of hands-on JavaScript frontend development, Strong knowledge of React.js, Strong knowledge of Node.js, Strong knowledge of NestJS, Experience with PHP, Experience with AWS, Experience with Docker, Experience with MySQL, Confident use of Git 📃 Skills: JavaScript, React.js, Node.js, NestJS, PHP, AWS, Docker, MySQL, Git, Salesforce, Contentful, Kubernetes, GraphQL, Jenkins, CI/CD 🏢 Description: Project overview The project is live and has been actively developed for over 5 years, with continuous feature enhancements and security improvements. All development is carried out on our side. Our client is a US‑based nonprofit organization developing an educational platform that supports students in learning computer science and building coding projects. The platform provides curriculum materials, teaching tools, progress tracking, collaboration features, and portfolio‑building capabilities. The mission of the platform is to help close the gender gap in the tech industry. Position overview We are looking for a Strong Middle/Senior Full Stack Developer (Node.js + React.js) to join our dynamic team. You will be involved in the design, development, and optimization of both frontend and backend functionality, working closely with a cross‑functional team on a long‑term product. Responsibilities Develop and maintain platform features using Node.js, React.js, and NestJS Participate in system design, architecture discussions, and technical decision‑making Improve platform performance, scalability, and security Implement integrations with third‑party systems (e.g., Salesforce, Contentful) Work closely with product managers, designers, and QA to deliver high‑quality features Write clean, maintainable, and well‑tested code Participate in code reviews and provide constructive feedback to the team Contribute to DevOps processes using AWS, Docker, and CI/CD tools Troubleshoot, debug, and resolve technical issues in both frontend and backend components Support continuous enhancement and modernization of the long‑running project Requirements 4+ years of professional software development experience 4+ years of hands‑on experience with JavaScript for frontend development Strong knowledge of: React.js, Node.js, NestJS Experience with PHP Experience working with AWS and Docker Experience with MySQL Confident use of Git Nice to have Solid understanding of Kubernetes Experience with GraphQL Familiarity with Jenkins and CI/CD automation Experience integrating with Salesforce and Contentful What We Offer: Vacation days : Up to 26 business days per year. 10 illness/special days off per year (fully paid, no medical papers needed) for all contract types Health and life insurance (Luxmed) MyBenefit platform with Multisport option Internal psychological support service English language classes from the first working day Access to external learning platforms : O’Reilly, LinkedIn Learning, Udemy, and a wide catalog of diverse internal training Flexible workplace : work from the office, from home, or choose a hybrid option Tech Skills Mentoring Program Opportunities to develop as a public speaker, mentor, or technical interviewer Fully paid idle (bench) when not involved in a project Certification reimbursement (AWS, GCP, Microsoft, etc.)

🏢 Summary: Fullstack Developer role focused on building and enhancing dynamic web applications using .NET on the backend and React on the frontend. The position involves developing robust services, implementing responsive UI components, and resolving complex technical issues. The goal is to strengthen the team’s capability to deliver high-performance, scalable applications. 🗂️ Requirements: 5+ years of fullstack development experience, .NET expertise for backend development, Strong React knowledge for frontend development, Experience with Web APIs (WCF, REST), Database management experience, Proficiency in HTML, JavaScript, CSS, Understanding of message queues 📃 Skills: .NET, React, WCF, REST, WebAPI, HTML, JavaScript, CSS, SQL, Databases, MessageQueues 🏢 Description: Summary: The ideal candidate is expected to function as a Fullstack Developer, contributing both front-end and back-end functionalities with a strong focus on .NET and React technologies. The primary goal is to enhance the team's capabilities in developing seamless, robust applications. Main Responsibilities: Engage in full-stack development to create dynamic web applications. Implement the front-end components using React. Develop back-end services using .NET. Communicate effectively with team members and stakeholders in English. Investigate and resolve complex technical problems proactively. Collaborate with team members to enhance application performance and usability. Key Requirements: 5+ years of experience in fullstack development. Expertise in .NET for backend development. Strong understanding of React for frontend development. Fluent communication skills in English. Knowledge of Web APIs (WCF and REST APIs). Familiarity with database management. Competence in HTML, JavaScript, and CSS. Understanding of message queues. Nice to Have: Experience with cloud services or platforms. Familiarity with CI/CD practices. Exposure to Agile methodologies.

🏢 Summary: Fullstack Developer role focused on building and enhancing dynamic web applications using .NET on the backend and React on the frontend. The position involves developing robust, high-performance solutions, integrating APIs, and resolving complex technical issues within a collaborative team environment. Strong emphasis is placed on delivering seamless end-to-end functionality. 🗂️ Requirements: 5+ years of fullstack development experience, .NET backend expertise, Strong React knowledge, Experience with WCF and REST APIs, Database management experience, Proficiency in HTML, JavaScript, CSS, Understanding of message queues, Fluent English communication 📃 Skills: .NET, C#, React, REST, WCF, SQL, HTML, JavaScript, CSS, Databases, MessageQueues, English 🏢 Description: Summary: The ideal candidate is expected to function as a Fullstack Developer, contributing both front-end and back-end functionalities with a strong focus on .NET and React technologies. The primary goal is to enhance the team's capabilities in developing seamless, robust applications. Main Responsibilities: Engage in full-stack development to create dynamic web applications. Implement the front-end components using React. Develop back-end services using .NET. Communicate effectively with team members and stakeholders in English. Investigate and resolve complex technical problems proactively. Collaborate with team members to enhance application performance and usability. Key Requirements: 5+ years of experience in fullstack development. Expertise in .NET for backend development. Strong understanding of React for frontend development. Fluent communication skills in English. Knowledge of Web APIs (WCF and REST APIs). Familiarity with database management. Competence in HTML, JavaScript, and CSS. Understanding of message queues. Nice to Have: Experience with cloud services or platforms. Familiarity with CI/CD practices. Exposure to Agile methodologies.

🏢 Summary: Fullstack Developer role focused on building scalable web applications using ASP.NET, C#, and React, with strong emphasis on API design, event-driven architecture, and cloud-native environments. The position involves end-to-end development, CI/CD practices, containerized deployments, and collaboration in agile teams. Ideal for engineers experienced in backend services, modern frontend ecosystems, and orchestration tools. 🗂️ Requirements: Strong experience with ASP.NET, Strong experience with C#, Experience building scalable backend services and APIs, Strong experience with React, Understanding of modern frontend architecture, Experience with API design, Experience with GitLab CI/CD, Experience with RabbitMQ, Experience with Docker, Experience with Kubernetes 📃 Skills: ASP.NET, C#, React, TanStack, Tailwind, Playwright, RabbitMQ, Docker, Kubernetes, GitLab, Linux, Unity, APIs, CI/CD 🏢 Description: Role Overview We are looking for a skilled Fullstack Developer with strong backend expertise in ASP.NET and C#, combined with modern frontend development using React. The role involves building scalable web applications, designing robust APIs, and contributing to cloud-native and event-driven architectures. The ideal candidate is comfortable working across the full stack, collaborates well in agile teams, and has an interest in modern tooling, orchestration, and frontend ecosystems. Core Responsibilities • Design, develop, and maintain scalable fullstack applications • Build and maintain backend services using ASP.NET and C# • Develop responsive and modern frontend applications using React • Design and integrate APIs and asynchronous communication flows • Collaborate with developers, designers, QA, and DevOps teams • Contribute to architecture discussions and technical decisions • Ensure code quality through testing, reviews, and CI/CD practices • Participate in deployment, monitoring, and troubleshooting activities Must-Have Skills Backend • Strong experience with ASP.NET • Strong experience with C# • Experience building scalable backend services and APIs Frontend • Strong experience with React • Good understanding of modern frontend architecture and component-based development Should-Have Skills • Experience with GitLab Pipelines / CI-CD • Experience with API design and best practices Frontend Libraries & Tooling • Experience with: o TanStack o Tailwind CSS o Playwright o AI agent development (Kiro, Claude, Cursor) Messaging & Async Communication • Experience with: o RabbitMQ o Event-driven and asynchronous communication patterns • Understanding of async workflows across frontend and backend systems Infrastructure & Orchestration • Experience with: o Docker o Kubernetes • Familiarity with containerized deployments and orchestration Nice-to-Have Skills • Interest or experience in Unity / game development • Strong Linux competence Preferred Qualifications • Experience working in agile development environments • Strong problem-solving and debugging skills • Understanding of scalable and maintainable software architecture • Good communication and collaboration skills • Passion for learning modern technologies and frameworks Tech Stack Summary Area Backend: ASP.NET, C# Frontend: React Frontend Libraries: TanStack, Tailwind, Playwright Messaging: RabbitMQ Infrastructure: Docker, Kubernetes CI/CD: GitLab Pipelines Additional: Linux, API Design, Unity

🏢 Summary: Full Stack Developer role focused on building, testing, and maintaining scalable and secure web applications across frontend and backend technologies. The position involves developing modern user interfaces, designing APIs, integrating third-party services, and ensuring high performance through testing and CI/CD practices. The role also contributes to architectural decisions and technical strategy. 🗂️ Requirements: Experience with React.js and Vue.js, Proficiency in HTML5, CSS3, JavaScript, TypeScript, Experience with .NET Core or Ruby backend development, Experience building RESTful and GraphQL APIs, Experience with PostgreSQL, MongoDB, or MySQL, Knowledge of Docker and CI/CD pipelines, Proficiency with Git version control, Experience with cloud platforms (AWS, Azure, or GCP), Experience with unit and integration testing frameworks 📃 Skills: React, Vue, HTML5, CSS3, JavaScript, TypeScript, .NET, Ruby, EntityFramework, GraphQL, REST, PostgreSQL, MongoDB, MySQL, Docker, Git, AWS, Azure, GCP, Jest, Mocha, JUnit, CICD 🏢 Description: Description The Full Stack Developer Role will need to be proficient in boththe relevant frontend and backend technologies to develop, test, and maintain scalable web applications, and will work across the entire tech stack, collaborating with cross-functionalteams to deliver robust, secure and performant digital solutions Responsibilities • Design, develop, test and maintain robust, scalable and secure web applications using the full tech stack • Develop user-friendly frontend interfaces for all users using modern JS frameworks • Build and maintain Restful and GraphQL APIs • Integrate third-party services, such as LMS, video conferencing, gamification APIs • Ensure code quality through code reviews, unit testing, and automated CI/CD pipelines • Optimize application performance, security, and scalability • Participate in architectural decisions and contribute to technical strategy • Ensure high performance, accessibility, and responsiveness across devices • Implement automated testing and CI/CD pipelines for efficient delivery Requirements • Frontend : React.js 18, Entity Framework Vue.js, HTML5, CSS3, JavaScript, TypeScript • Backend: MS .NET 8 Core / Ruby • Database : PostgreSQL, MongoDB, MySQL, or similar • DevOps : Docker, CI/CD, Git, cloud platforms (AWS, Azure, GCP) • Testing : Unit and integration testing frameworks (e.g., Jest, Mocha, JUnit Nice to have • Experience with WebRTC, LTI standards, SCORM/xAPI, or real-time systems (e.g., live quizzes, video  classrooms) • Knowledge of learning science, instructional design, or accessibility standards (e.g., WCAG) • Familiarity with tools like Moodle, Canvas, Zoom SDK, or Google Classroom integration • Prior experience in the EdTech domain (e-learning platforms, digital classrooms, LMS) • Familiarity with tools like Moodle, Canvas, Zoom SDK, or Google Classroom integration • Experience with Rabbit MQ middleware • Experience with Tailwind

🏢 Summary: Full Stack Developer role focused on building, testing, and maintaining scalable and secure web applications across frontend and backend. The position involves developing modern user interfaces, implementing APIs, integrating third-party services, and ensuring high performance through automated testing and CI/CD. The role also contributes to architectural decisions and technical strategy. 🗂️ Requirements: Proficiency in React.js and Vue.js, Strong knowledge of HTML5, CSS3, JavaScript, TypeScript, Experience with .NET Core or Ruby backend development, Experience building RESTful and GraphQL APIs, Experience with PostgreSQL, MongoDB, or MySQL, Experience with Docker and CI/CD pipelines, Proficiency with Git version control, Experience with AWS, Azure, or GCP, Experience with unit and integration testing frameworks 📃 Skills: React, Vue, HTML5, CSS3, JavaScript, TypeScript, .NET, Ruby, EntityFramework, REST, GraphQL, PostgreSQL, MongoDB, MySQL, Docker, CICD, Git, AWS, Azure, GCP, Jest, Mocha, JUnit 🏢 Description: Description The Full Stack Developer Role will need to be proficient in boththe relevant frontend and backend technologies to develop, test, and maintain scalable web applications, and will work across the entire tech stack, collaborating with cross-functionalteams to deliver robust, secure and performant digital solutions Responsibilities • Design, develop, test and maintain robust, scalable and secure web applications using the full tech stack • Develop user-friendly frontend interfaces for all users using modern JS frameworks • Build and maintain Restful and GraphQL APIs • Integrate third-party services, such as LMS, video conferencing, gamification APIs • Ensure code quality through code reviews, unit testing, and automated CI/CD pipelines • Optimize application performance, security, and scalability • Participate in architectural decisions and contribute to technical strategy • Ensure high performance, accessibility, and responsiveness across devices • Implement automated testing and CI/CD pipelines for efficient delivery Requirements • Frontend : React.js 18, Entity Framework Vue.js, HTML5, CSS3, JavaScript, TypeScript • Backend: MS .NET 8 Core / Ruby • Database : PostgreSQL, MongoDB, MySQL, or similar • DevOps : Docker, CI/CD, Git, cloud platforms (AWS, Azure, GCP) • Testing : Unit and integration testing frameworks (e.g., Jest, Mocha, JUnit Nice to have • Experience with WebRTC, LTI standards, SCORM/xAPI, or real-time systems (e.g., live quizzes, video  classrooms) • Knowledge of learning science, instructional design, or accessibility standards (e.g., WCAG) • Familiarity with tools like Moodle, Canvas, Zoom SDK, or Google Classroom integration • Prior experience in the EdTech domain (e-learning platforms, digital classrooms, LMS) • Familiarity with tools like Moodle, Canvas, Zoom SDK, or Google Classroom integration • Experience with Rabbit MQ middleware • Experience with Tailwind

🏢 Summary: Full Stack Developer role focused on building, testing, and maintaining scalable and secure web applications across the entire tech stack. The position involves developing modern frontend interfaces, robust backend services, and APIs, while ensuring high performance, quality, and automated delivery through CI/CD pipelines. The role also includes integration with third-party services and contribution to architectural and technical decisions. 🗂️ Requirements: Proficiency in React.js 18, Vue.js, HTML5, CSS3, JavaScript, TypeScript, Experience with MS .NET 8 Core or Ruby, Experience building RESTful and GraphQL APIs, Experience with PostgreSQL, MongoDB, MySQL or similar databases, Experience with Docker, CI/CD pipelines, Git, and cloud platforms (AWS, Azure, or GCP), Experience with unit and integration testing frameworks 📃 Skills: React, Vue, HTML5, CSS3, JavaScript, TypeScript, .NET, Ruby, PostgreSQL, MongoDB, MySQL, Docker, CI/CD, Git, AWS, Azure, GCP, Jest, Mocha, JUnit, GraphQL, REST 🏢 Description: Description The Full Stack Developer Role will need to be proficient in boththe relevant frontend and backend technologies to develop, test, and maintain scalable web applications, and will work across the entire tech stack, collaborating with cross-functionalteams to deliver robust, secure and performant digital solutions Responsibilities • Design, develop, test and maintain robust, scalable and secure web applications using the full tech stack • Develop user-friendly frontend interfaces for all users using modern JS frameworks • Build and maintain Restful and GraphQL APIs • Integrate third-party services, such as LMS, video conferencing, gamification APIs • Ensure code quality through code reviews, unit testing, and automated CI/CD pipelines • Optimize application performance, security, and scalability • Participate in architectural decisions and contribute to technical strategy • Ensure high performance, accessibility, and responsiveness across devices • Implement automated testing and CI/CD pipelines for efficient delivery Requirements • Frontend : React.js 18, Entity Framework Vue.js, HTML5, CSS3, JavaScript, TypeScript • Backend: MS .NET 8 Core / Ruby • Database : PostgreSQL, MongoDB, MySQL, or similar • DevOps : Docker, CI/CD, Git, cloud platforms (AWS, Azure, GCP) • Testing : Unit and integration testing frameworks (e.g., Jest, Mocha, JUnit Nice to have • Experience with WebRTC, LTI standards, SCORM/xAPI, or real-time systems (e.g., live quizzes, video  classrooms) • Knowledge of learning science, instructional design, or accessibility standards (e.g., WCAG) • Familiarity with tools like Moodle, Canvas, Zoom SDK, or Google Classroom integration • Prior experience in the EdTech domain (e-learning platforms, digital classrooms, LMS) • Familiarity with tools like Moodle, Canvas, Zoom SDK, or Google Classroom integration • Experience with Rabbit MQ middleware • Experience with Tailwind

🏢 Summary: Full-Stack Developer role focused on building and enhancing business applications using C#/.NET on the backend and React (18+) on the frontend. The position involves developing new features, maintaining and improving legacy code, and contributing to solution design within an Agile/Scrum team. Strong emphasis on backend expertise, frontend development, and architectural best practices. 🗂️ Requirements: 5+ years of experience with .NET and C#, 3+ years of experience with React (18+), Strong knowledge of .NET Framework, .NET Standard, .NET Core/.NET, Experience with debugging, profiling and performance analysis, Understanding of DDD, Clean Code and SOLID principles, Knowledge of architectural patterns and asynchronous communication, Good command of T-SQL, Experience with SQL Server Management Studio (SSMS), Experience with Visual Studio 📃 Skills: C#, .NET, React, TSQL, SQLServer, SSMS, VisualStudio, DDD, SOLID, CleanCode, Scrum, Debugging, Profiling, Architecture, Asynchronous 🏢 Description: We’re looking for an experienced Full-Stack Developer to build and evolve business applications using C#/.NET on the backend and React on the frontend. You’ll work closely with a cross-functional team (QA, Analysts, Product Owner) in an Agile/Scrum environment, contributing to both new development and improvements to existing (including legacy) codebases. Key responsibilities: Develop software in C# based on functional and technical documentation Build and maintain the frontend using React (18+) Analyse and improve existing code, including legacy components Contribute to solution design and architecture Collaborate daily with developers, testers, analysts and the Product Owner in Scrum Requirements: 5+ years of experience building applications with .NET / C# 3+ years of experience building applications with React Strong knowledge of C# (.NET Framework, .NET Standard, .NET Core/.NET) React experience with modern versions (React 18+) Practical skills in debugging, profiling and performance analysis Understanding of DDD, Clean Code, SOLID Knowledge of architectural patterns and asynchronous communication Good command of T-SQL and SQL Server Management Studio (SSMS) Experience working with Visual Studio Nice to have Experience building views/UI for mobile applications Background in projects for the financial sector Test automation experience (e.g., Postman, Playwright) Familiarity with WCAG accessibility standards

🏢 Summary: Full Stack Developer role with a strong frontend focus, responsible for building scalable modern web applications using React and TypeScript while contributing to backend services in .NET. The position involves delivering end-to-end features, integrating REST APIs, and ensuring high performance across frontend and backend layers in an agile environment. 🗂️ Requirements: Completed degree in Computer Science or related technical field, Strong commercial experience with React, Strong commercial experience with TypeScript, Solid understanding of modern frontend architecture and performance optimization, Experience building scalable and maintainable web applications, Good understanding of REST APIs and backend integration, Experience with C#, Experience with .NET development, Experience working in agile development environments, Understanding of software development lifecycle 📃 Skills: React, TypeScript, C#, .NET, REST, APIs, Agile, SDLC 🏢 Description: Responsibilities We are looking for a Full Stack Developer with a strong frontend focus who wants to work on modern web applications in an international environment. You will design and develop scalable business applications, primarily using React and TypeScript , while also contributing to backend services and integrations. You collaborate closely with product owners, architects, and engineering teams to deliver end-to-end features across the full stack. Your key responsibilities include: Design, develop, and maintain modern web applications using React and TypeScript . Implement responsive, user-friendly and high-performance frontend solutions. Collaborate with backend engineers and architects to deliver end-to-end features . Develop and maintain backend services and APIs using .NET technologies. Troubleshoot , debug , and optimize application performance across frontend and backend layers. Work in an agile environment with cross-functional and international teams. Support application deployment , maintenance , and continuous improvement of systems. Contribute to technical discussions and help ensure code quality and maintainability . Benefits Motivizer Benefits Platform to choose and manage all your benefits in one place. You receive a budget (550 PLN monthly). You can choose medical care package, meal tickets, sports cards (we have Multisport and on preferential terms, we have membership cards to one of the most popular Gyms), cinema tickets, shop vouchers, discounts and many more. Language Courses – you'll have access to a multi-language learning platform enabling you to practice your language skills and learn new ones! Regular and systematic further training opportunities - both internally and from external providers. We support your ongoing learning and development. Cooperation within an internal community is our everyday reality. We have networking events, coding challenges, and company parties for different occasions. Qualifications Completed university degree in Computer Science or a comparable technical field. Strong experience with React and TypeScript in production environments. Solid understanding of modern frontend architecture , performance , and best practices . Experience building scalable and maintainable web applications . Good understanding of REST APIs and backend integration concepts. Experience with C# and . NET development. Familiarity with agile methodologies and software development lifecycle . Fluent English and Polish communication skills and ability to work in international teams. Nice to have: Experience with MongoDB or other NoSQL databases. Knowledge of GraphQL and advanced API patterns. Exposure to Microsoft Azure and cloud - native architectures . Understanding of DevOps practices and CI/CD pipelines . Experience working in enterprise - scale or distributed systems environments . About Cluster Reply Cluster Reply is the Reply Group company specializing in consulting and system integration of Microsoft technologies. As a Microsoft partner, Cluster Reply is active in Germany, Austria and Switzerland and works within the Reply network with sister companies in Brazil, Great Britain, Italy as well as the USA. The company focuses on innovation and supports customers in their digital transformation. The solutions range from on-premises to cloud applications in the areas of modern workplace and security, business applications, applications and infrastructure as well as data and artificial intelligence.

🏢 Summary: Senior Full-Stack Developer role focused on enhancing a platform using React and TypeScript on the frontend and .NET/C# with SQL Server on the backend. The position emphasizes strong frontend expertise while maintaining sufficient backend knowledge for independent task execution. Experience with legacy systems is considered an advantage. 🗂️ Requirements: 5+ years full-stack development experience (Mid) or 10+ years (Senior), Proficiency in React, Proficiency in TypeScript, Strong knowledge of modern JavaScript, Solid knowledge of C# and .NET, Ability to work with SQL Server 📃 Skills: React, TypeScript, JavaScript, C#, .NET, SQL, SQLServer, ClassicASP 🏢 Description: Summary: A senior full-stack developer position focused on enhancing our platform through modern technologies, primarily using React and TypeScript on the frontend and .NET/C# with SQL Server on the backend. Main Responsibilities: Strengthen the focus on React and TypeScript as the primary and most critical skills, with a solid foundation in modern JavaScript. Utilize .NET/C# and SQL Server as supporting skills to ensure self-sufficiency in day-to-day tasks without primary responsibility for complex backend or database optimization. Leverage knowledge of legacy technologies, such as Classic ASP, for understanding existing logic as a nice-to-have skill. Key Requirements: At least 5 years of experience (Mid-level) or 10 years (Senior-level) in full-stack development. Proficiency in React and TypeScript. Solid foundation in modern JavaScript and C# / .NET. Nice to Have: Experience with legacy systems like Classic ASP.