Back-End Developer (.NET/C#)

🏢 Summary: Full Stack Development Lead role focused on delivering end-to-end solutions using React and C# .NET Core in a cloud-driven, microservices-based environment. The position combines hands-on development with architectural input and technical leadership in a fully remote B2B setup. The role involves close collaboration with cross-functional teams and contribution to modern DevOps and data workflows. 🗂️ Requirements: Proven full-stack experience with React, TypeScript, C# .NET Core, Strong knowledge of microservices architecture, Understanding of distributed systems, Experience with CI/CD pipelines, Experience with cloud platforms (Azure preferred), Experience with containers, Familiarity with DevOps practices, Ability to design APIs and event-driven components 📃 Skills: React, TypeScript, C#, .NET, Microservices, CI/CD, Azure, Docker, DevOps, PySpark, PowerBI, APIs 🏢 Description: Start Date: ASAP / Within 1 Month / Flexible Work Model: 100% remote Contract Type: B2B (160-180 PLN/h + VAT) We are looking for an experienced Full Stack Development Lead who will take ownership of end‑to‑end solutions across React and C# .NET Core while contributing to technical direction and supporting a collaborative engineering culture. This role is ideal for a strong Senior Full Stack Developer who is ready to expand into leadership responsibilities, work closely with cross‑functional teams, and influence architectural decisions in a modern, cloud‑driven environment. Expectations Proven experience in full‑stack development using React, TypeScript, and C# .NET Core. Good understanding of microservices , distributed systems, and CI/CD pipelines. Exposure to cloud platforms (Azure preferred), containers, and modern DevOps practices. Experience with data workflows (pyspark) or BI solutions (Power BI) is a strong advantage. Ability to collaborate with technical and business stakeholders and take initiative in solution design. Responsibilities Contribute to the design and delivery of full‑stack applications using React and C# .NET Core. Support architectural discussions around microservices, APIs, and event‑driven components. Collaborate with data engineers on pyspark workflows and Power BI reporting enhancements. Promote engineering best practices, code quality, and maintainable development patterns. Mentor team members and support planning, collaboration, and continuous improvement efforts. What We Offer Medicover healthcare package Multisport card Access to an e-learning platform Group life insurance

🏢 Summary: Full Stack Developer role focused on building scalable, cloud-native applications using React and C# .NET Core in a capital markets environment. The position involves developing microservices, REST APIs, data pipelines, and analytical solutions supporting credit and market risk domains. 100% remote B2B contract with flexible start date. 🗂️ Requirements: 4-5+ years of full stack development experience, Strong expertise in React, Strong expertise in C#, Experience with .NET Core, Experience with microservices architecture, Experience with event-driven architecture, Experience with distributed systems, Experience building REST APIs, Hands-on experience with Python, Experience with PySpark, Experience with Power BI, Experience with data modeling, Experience in credit risk and market risk domains 📃 Skills: React, C#, .NETCore, Microservices, REST, TypeScript, Python, PySpark, PowerBI, DataModeling, DistributedSystems, EventDriven, Cloud 🏢 Description: Start Date: ASAP / Within 1 Month / Flexible Work Model: 100% remote Contract Type: B2B (140-160 PLN/h + VAT) We are looking for a highly skilled Full Stack Developer with deep expertise in React for frontend development and C# .NET Core for backend services. This role requires hands‑on experience building scalable, cloud‑native systems, along with strong exposure to capital markets, especially within credit risk and market risk domains. Expectations Minimum 4-5 years of professional software development experience across frontend and backend technologies. Strong expertise in React, C# .NET Core , microservices, event‑driven architecture, and distributed systems. Hands‑on experience with Python (pyspark), Power BI dashboards, data modeling, and analytical reporting. Responsibilities Develop and maintain full stack applications using React, C# .NET Core, and modern cloud‑native technologies. Build scalable backend services, REST APIs, and microservices with a focus on performance and resilience. Implement modular, accessible, and high‑quality frontend components using React and TypeScript. Collaborate with business and risk experts to deliver solutions in credit risk, market risk, and capital markets workflows. Work with Python (pyspark) to build data pipelines, transformations, and analytics processes. What We Offer Medicover healthcare package Multisport card Access to an e-learning platform Group life insurance

🏢 Summary: Fully remote .NET Developer role focused on designing and developing modern backend systems based on microservices architecture. The position involves building scalable REST APIs, implementing event-driven solutions, and deploying cloud-native applications on Microsoft Azure using containerized environments. The role also includes working with enterprise integrations, security standards, and database optimization within Agile teams. 🗂️ Requirements: Experience with .NET Core and .NET 8/9, Experience with ASP.NET Core, Experience in microservices architecture, Experience building RESTful APIs, Experience with Apache Kafka, Experience with Docker and Kubernetes, Experience with Microsoft Azure cloud services, Knowledge of OAuth 2.0 and OpenID Connect, Experience with SQL Server and Oracle, Knowledge of event-driven architecture, Experience with container orchestration and Helm, Understanding of SOLID principles and design patterns 📃 Skills: .NET, ASP.NET, Kafka, Docker, Kubernetes, OpenShift, Helm, Azure, SQL, Oracle, OAuth2, OIDC, TLS, AzureAD, REST 🏢 Description: Job Description We are looking for an experienced .NET Developer to design and develop modern backend solutions based on microservices architecture. The role is fully remote in Poland. Responsibilities: Design and develop microservices using .NET (Core / 8/9) and ASP.NET Core Build scalable RESTful APIs and backend services Implement event-driven architecture using Apache Kafka Deploy and maintain applications in containerized environments using Docker, Kubernetes, OpenShift, and Helm Design cloud-native solutions leveraging Microsoft Azure services Integrate applications with enterprise systems and external data sources Apply SOLID principles and modern design patterns Implement security standards including OAuth 2.0, OpenID Connect (OIDC), TLS, and Azure AD (Entra ID) Work with SQL Server and Oracle databases , including performance optimization Conduct code reviews and mentor junior developers Collaborate within Agile development teams Tech Stack: .NET Core / .NET 8/9 ASP.NET Core Apache Kafka Docker, Kubernetes, OpenShift, Helm Microsoft Azure (cloud-native services) SQL Server, Oracle OAuth 2.0, OpenID Connect, Azure AD (Entra ID) REST APIs, microservices architecture

🏢 Summary: 100% remote B2B opportunity to lead a development team in building and maintaining scalable applications within an agile environment. The role combines hands-on full-stack development with strategic technical leadership, focusing on robust system architecture and faster delivery of new solutions. Long-term cooperation with a two-stage recruitment process including a technical test. 🗂️ Requirements: Proficiency in .NET, Proficiency in C#, Experience in full-stack development, Experience with front-end technologies, Experience with document-based databases, Knowledge of event-based messaging frameworks, Experience with cloud services, Experience with containerization, Ability to lead development teams, Experience working in agile environment 📃 Skills: .NET, C#, Angular, MongoDB, Cloud, Docker, Microservices, REST, Git 🏢 Description: Work model: 100% remote Start date: Flexible Rate: up to 215 PLN/h netto + VAT Contract : B2B, long-term cooperation (12-month contract up front + extensions) Recruitment process : 2 stages, including a technical test estimated to take 2-4 hours. Summary: The role focuses on leading the development team to create new solutions and maintain systems within an agile environment, emphasizing the importance of robust applications and strategic direction. Main Responsibilities: Lead the development team in creating and maintaining applications. Adopt wider technology practices and address the speed of new application delivery. Engage in hands-on development while guiding the strategic direction of projects. Collaborate with teams to gather specifications and perform technical analysis. Navigate complex systems and ensure they are built to scale. Manage developer quality and capacity amidst organizational constraints. Key Requirements: Proficient in .NET and C#. Experience with full-stack development, including front-end technologies. Familiarity with document-based databases. Knowledge of event-based messaging frameworks. Experience with cloud services and containerization. Nice to Have: Prior experience in the banking or financial services sector. Familiarity with Angular or other modern front-end frameworks. Experience with MongoDB or similar environments. Other Details: Environment: .NET, C#, Angular, MongoDB, moving towards cloud solutions. Team Structure: Full Stack Developers working closely with Business Analysts.

🏢 Summary: B2B remote role for an experienced Software Engineer focused on building cross-platform components using C++, C#, and Kotlin Multiplatform. The position involves integrating native C++ modules with .NET applications and developing secure Windows-based functionality. You will contribute hands-on to designing and delivering scalable, high-quality technical solutions. 🗂️ Requirements: Commercial experience with C++, Experience with C# and native library integration, Ability to create and maintain NuGet packages, Knowledge of Windows programming, Experience with security modules, Experience with Kotlin Multiplatform or willingness to learn 📃 Skills: C++, C#, Kotlin, KotlinMultiplatform, .NET, NuGet, Windows, DLL 🏢 Description: Start Date: ASAP / Within 1 Month / Flexible Work Model: 100% remote Contract Type: B2B (180-200 PLN/h + VAT) We are looking for an experienced software engineer with strong skills in C++, C#, and Kotlin Multiplatform to join our engineering team. You will work on cross‑platform components, integrate native code with .NET applications, and contribute to developing secure and reliable features for modern systems. The role involves hands‑on coding, problem‑solving, and collaborating closely with other engineers to deliver high‑quality technical solutions. Expectations Solid commercial experience with C++ development , ideally on Windows. Practical experience using C# and integrating native libraries. Ability to create and maintain C# NuGet packages. Familiarity with Windows programming concepts, including security modules. Experience with Kotlin Multiplatform or willingness to learn it quickly. Responsibilities Develop cross‑platform components using C++, C#, and Kotlin Multiplatform. Integrate native C++ modules (DLLs) with C# applications. Build and maintain reusable C# libraries and NuGet packages. Implement and support Windows‑based functionality, including security‑related modules. Collaborate with the engineering team to design, test, and deliver scalable solutions. What We Offer Medicover healthcare package Multisport card Access to an e-learning platform Group life insurance

🏢 Summary: Long-term backend role focused on building and maintaining system integrations in an Azure-native environment using C#/.NET. The position involves developing APIs and microservices, working with cloud services, and improving CI/CD and Infrastructure as Code solutions within an Agile/SAFe setup. The project connects internal and external systems to support real business operations. 🗂️ Requirements: Minimum 3 years of experience as a Backend or .NET Developer, Strong experience with C# and .NET 6+, Experience building and maintaining system integrations, Hands-on work with REST APIs, message queues, FTP, microservices, Experience with Azure or other cloud platforms (AWS, GCP), Basic knowledge of Infrastructure as Code, Experience with CI/CD pipelines, Experience working in distributed systems or microservices architecture 📃 Skills: C#, .NET, Azure, AWS, GCP, REST, APIs, Microservices, MessageQueues, FTP, Terraform, Bicep, Pulumi, AzurePipelines, GitHubActions, GitLabCI, Jenkins, TeamCity 🏢 Description: Do you want to build integrations that power real business operations across the globe? Are you ready to work in an Azure-native environment where you can grow your skills in cloud, messaging, and microservices? If you enjoy learning on the job and working closely with business and Scrum teams, this project could be a great fit. Join a long-term integration team in Poland, contributing to solutions that connect systems for clients, partners, and internal teams. Key responsibilities Develop backend applications in C# / .NET Build and maintain integrations between systems (APIs, messaging, microservices) Work with cloud services (mainly Azure) Support and improve CI/CD pipelines and Infrastructure as Code (IaC) solutions Troubleshoot and resolve integration issues Collaborate with other application teams in an Agile/SAFe-based environment Ideal candidate profile At least 3 years of experience as a backend or .NET developer Practical experience with C# and .NET (6+) Experience with system integrations (REST APIs, message queues, FTP, microservices) Familiarity with cloud platforms (Azure preferred, AWS/GCP acceptable) Basic understanding of Infrastructure as Code (Azure Bicep, Terraform, Pulumi) and CI/CD pipelines (Azure Pipelines, GitHub Actions, GitLab CI/CD, Jenkins, TeamCity) Comfortable working in a distributed systems / microservices environment Team-oriented, communicative, and eager to learn from both business and technical teams Conditions Location: Gdańsk (Olivia Centre) Work model: Hybrid (2-3 days in the office) Employment type: B2B Project duration: Long-term cooperation expected; the first contract for 6-12 months Salary: 100-150 PLN/h Recruitment steps Initial call with a KUBO recruiter Interviews with the client Decision and feedback

🏢 Summary: Long-term remote B2B contract for a technical leader responsible for guiding a development team in building and maintaining scalable applications within an agile environment. The role combines hands-on .NET development with strategic oversight, technical analysis, and quality management. Focus is on delivering robust, cloud-oriented solutions and improving application delivery speed. 🗂️ Requirements: Proficiency in .NET and C#, Experience in full-stack development, Experience with front-end technologies, Experience with document-based databases, Knowledge of event-based messaging frameworks, Experience with cloud services, Experience with containerization, Ability to lead development team, Experience in building scalable systems 📃 Skills: .NET, C#, Angular, MongoDB, Cloud, Docker, Messaging, SQL 🏢 Description: Work model: 100% remote Start date: 30.06.2026 Rate: 160-180 PLN/h netto + VAT Contract : B2B, long-term cooperation (12-month contract up front + extensions) Recruitment process : 2 stages, including a technical test estimated to take 2-4 hours. Summary: The role focuses on leading the development team to create new solutions and maintain systems within an agile environment, emphasizing the importance of robust applications and strategic direction. Main Responsibilities: Lead the development team in creating and maintaining applications. Adopt wider technology practices and address the speed of new application delivery. Engage in hands-on development while guiding the strategic direction of projects. Collaborate with teams to gather specifications and perform technical analysis. Navigate complex systems and ensure they are built to scale. Manage developer quality and capacity amidst organizational constraints. Key Requirements: Proficient in .NET and C#. Experience with full-stack development, including front-end technologies. Familiarity with document-based databases. Knowledge of event-based messaging frameworks. Experience with cloud services and containerization. Nice to Have: Prior experience in the banking or financial services sector. Familiarity with Angular or other modern front-end frameworks. Experience with MongoDB or similar environments. Other Details: Environment: .NET, C#, Angular, MongoDB, moving towards cloud solutions. Team Structure: Full Stack Developers working closely with Business Analysts.

🏢 Summary: Technical leadership role focused on driving the development and maintenance of scalable .NET-based applications in an agile environment. The position combines hands-on full-stack development with strategic oversight of architecture, quality, and delivery speed. It involves close collaboration with cross-functional teams to build robust, cloud-oriented solutions. 🗂️ Requirements: Proficiency in .NET and C#, Experience in full-stack development, Knowledge of front-end technologies, Experience with document-based databases, Knowledge of event-based messaging frameworks, Experience with cloud services, Experience with containerization, Ability to design scalable systems, Experience leading development teams 📃 Skills: .NET, C#, Angular, MongoDB, Cloud, Docker, Kubernetes, Microservices, REST, Git 🏢 Description: Work model: 100% remote Start date: 30.06.2026 Rate: 160-180 PLN/h netto + VAT Contract : B2B, long-term cooperation (12-month contract up front + extensions) Recruitment process : 2 stages, including a technical test estimated to take 2-4 hours. Summary: The role focuses on leading the development team to create new solutions and maintain systems within an agile environment, emphasizing the importance of robust applications and strategic direction. Main Responsibilities: Lead the development team in creating and maintaining applications. Adopt wider technology practices and address the speed of new application delivery. Engage in hands-on development while guiding the strategic direction of projects. Collaborate with teams to gather specifications and perform technical analysis. Navigate complex systems and ensure they are built to scale. Manage developer quality and capacity amidst organizational constraints. Key Requirements: Proficient in .NET and C#. Experience with full-stack development, including front-end technologies. Familiarity with document-based databases. Knowledge of event-based messaging frameworks. Experience with cloud services and containerization. Nice to Have: Prior experience in the banking or financial services sector. Familiarity with Angular or other modern front-end frameworks. Experience with MongoDB or similar environments. Other Details: Environment: .NET, C#, Angular, MongoDB, moving towards cloud solutions. Team Structure: Full Stack Developers working closely with Business Analysts.

🏢 Summary: B2B contract for a Mid/Senior FullStack Engineer to modernize and migrate legacy .NET applications to a modular, cloud-native Azure architecture in the banking sector. The role combines backend development in .NET with frontend work in React, focusing on refactoring legacy systems, building scalable APIs, and implementing CI/CD and observability practices. Hybrid work model with strong influence on architectural decisions and cloud migration. 🗂️ Requirements: 5+ years of commercial experience with C# and .NET (Framework and .NET Core/6+), Strong proficiency in EF Core and MSSQL (query tuning, transactions, indexing), Commercial experience with React and TypeScript, Experience building and securing REST APIs (authentication, versioning, validation), Familiarity with Azure services (App Service, Functions, SQL, Service Bus, Storage), Experience with automated testing (unit, integration, contract, E2E), Experience with CI/CD pipelines (Azure DevOps or GitHub Actions), Ability to work with legacy .NET codebases (ASP.NET MVC, Razor, WPF, WinForms), English at B2+ level 📃 Skills: C#, .NET, .NETCore, .NET6, .NET8, EFCore, MSSQL, T-SQL, React, TypeScript, REST, Azure, AppService, AzureFunctions, AzureSQL, ServiceBus, AzureStorage, xUnit, Jest, Playwright, Cypress, Git, AzureDevOps, GitHubActions, ASP.NET, MVC, Razor, WPF, WinForms, DDD, CleanArchitecture 🏢 Description: We are looking for FullStack Engineer (.NET & React) Location: Kraków / Hybrid (7 days in the office per month) Contract Type: B2B Contract Seniority: Mid / Senior About the Project Join a high-impact modernization initiative for a leading player in the banking sector . We are transforming a portfolio of approximately a dozen .NET applications and MSSQL databases into a modular, cloud-native Azure architecture. As a FullStack Engineer, you will play a dual role: evolving existing production services (including legacy UI and desktop components) while systematically extracting business logic to re-implement it into a modern, scalable ecosystem. This is a unique opportunity to influence the transition from monolithic architectures to high-performance, distributed cloud services. Your Responsibilities Design & Development: Build backend services and APIs using .NET 6/8 following Clean Architecture and DDD patterns. Frontend Evolution: Develop and maintain React + TypeScript frontends, managing the incremental migration from legacy UI modules. Modernization: Read, refactor, and extract complex business logic from legacy .NET codebases and T-SQL stored procedures. Quality Assurance: Write and maintain comprehensive automated tests (Unit, Integration, Contract, and E2E). DevOps & Observability: Create CI/CD pipelines (Azure DevOps/GitHub Actions) and instrument services for deep observability (metrics, logs, distributed traces). Collaboration: Participate in domain modeling, architecture discussions, and Agile ceremonies with Architects and Product Owners. Skills & Experience We Require Experience: 5+ years of commercial experience with C# and the .NET ecosystem (both Framework and .NET Core/6+). Database Expertise: Strong proficiency in EF Core and MSSQL (including query tuning, transactions, and indexing). Frontend: Solid production experience with React and TypeScript. Web Services: Practical experience in building and securing REST APIs (Auth, Versioning, Validation). Cloud: Familiarity with Azure services (App Service, Functions, SQL, Service Bus, Storage). Testing & Tooling: Experience with xUnit, Jest, and Playwright/Cypress, as well as disciplined Git practices. Legacy Handling: The ability to read and reason about legacy codebases (ASP.NET MVC, Razor, WPF, or WinForms). Communication: English at a B2+ level for technical documentation and team collaboration. Nice to Have Experience with Infrastructure as Code (Terraform or Bicep). Knowledge of Docker and Kubernetes (AKS). Background in migrating monoliths to microservices. Azure Developer Associate certification. What We Offer Impact: Real influence on the architecture and the cloud migration roadmap. Autonomy: Direct collaboration with Tech Leads and Architects in a flat structure. Modern Stack: Opportunity to work with the latest .NET versions (6/8) and React. Efficiency: Fast technical onboarding with immediate access to repos, CI/CD pipelines, and monitoring tools. Flexible Hybrid Model: Remote-first approach with only 7 planned days in the Kraków office per month. Benefits : Luxmed and Multisport Card

🏢 Summary: B2B opportunity for an experienced .NET Back-End Developer to build modern, scalable cloud-based solutions using C# and Azure. The role focuses on designing high-performance services, working with CosmosDB, and collaborating in an Agile team with exposure to AI-assisted development tools. This is a fully remote position with competitive hourly rates and long-term cooperation. 🗂️ Requirements: 5+ years of professional experience in .NET development, Strong experience with C#, Proven experience with Azure services, Experience with CosmosDB, Experience with TypeScript or JavaScript, Bachelor’s degree in Computer Science or related field, Ability to align with US-based team working hours, English language proficiency 📃 Skills: .NET, C#, Azure, CosmosDB, TypeScript, JavaScript, AI, Playwright, Selenium, Drupal 🏢 Description: For our client from the technology and industrial solutions sector, we are looking for a .NET Back-End Developer to join a talented development team working on modern, scalable software solutions. Responsibilities: Design, develop, and maintain high-performance back-end services using .NET and C#. Work extensively with Azure cloud services and CosmosDB to build scalable and resilient solutions. Collaborate with front-end developers, product owners, and other team members to integrate back-end services. Participate in code reviews, architectural discussions, sprint planning, and other Agile ceremonies. Use modern development tools and practices to improve productivity, code quality, and maintainability. Explore and apply AI-assisted tools where appropriate to support development, documentation, troubleshooting, and workflow efficiency. Contribute to improving development processes, engineering practices, and team knowledge sharing. Be a proactive problem-solver and continuous learner, staying current with relevant technologies and industry trends. Requirements: Application Development Experience: 5+ years of professional experience in .NET development. Cloud Development Expertise: Proven experience with C#, Azure services, and CosmosDB. Scripting / Front-End Knowledge: Experience with TypeScript preferred, or JavaScript. AI Tool Familiarity: Interest in or hands-on experience using AI tools to support software development, productivity, documentation, research, or troubleshooting. Educational Background: Bachelor’s degree in Computer Science or a related field. Flexibility: Ability to align somewhat with US-based team working hours. Communication: English language proficiency. Stack: Cloud: Azure, CosmosDB Back-End: .NET, C# Scripting / Tooling: TypeScript preferred, JavaScript acceptable Productivity / AI Tools: Familiarity with AI-assisted development or productivity tools is a plus Nice to have: Domain Knowledge: Background in Electrical Engineering or a related technical field. Background or interest in analog and mixed-signal hardware design. Knowledge of hardware or system simulation concepts. CMS Knowledge: Familiarity with Drupal. Test Automation Exposure: Familiarity with tools like Playwright or Selenium. Quality Mindset: Prior QA experience or understanding of QA methodologies is welcome. Offer: Cooperation based on a B2B contract and rate: 140-170 PLN/hour 100% remote work The support of a dedicated mentor. In the relationship, we focus on direct communication. When you join speedapp, you will be put in touch with a dedicated mentor who will make sure that you enjoy working with us and with the client. Events and integration meetings, as well as participation in various initiatives, e.g., sports. Access to the benefits offering (medical care, Multisport card). About Speedapp At speedapp, we believe that an organization is only as good as the people who make it up. We are a team of IT experts and other professionals working for our clients around the world (including Israel, Austria, USA). We go far beyond the HR category. We build IT teams and also help manage them. 👉 10 years of experience 👉 +100 clients worldwide +300 hires per year 💎 We have won the prestigious "Forbes Diamonds" award four times (2022, 2023, 2024, 2025). We are a member of the European Fast Growth Icons network and FinTech Poland. We are ranked 18th among the 100 fastest growing companies 2023 by Clutch.