Senior .Net Developer

🏢 Summary: Short-term contract role for a .NET Developer to build and maintain scalable backend systems in the energy and logistics domain using microservices architecture. The work focuses on developing REST APIs, system integrations, and high-performance services with modern technologies. The project emphasizes AI-supported development and offers potential extension and growth into architectural responsibilities. 🗂️ Requirements: 2.5–4+ years of experience as a .NET Developer, Strong knowledge of .NET 8, Strong knowledge of ASP.NET Core API, Experience with Entity Framework Core, Experience with SQL Server, Experience with Redis, Experience with RabbitMQ, Experience with Docker, Understanding of microservices architecture, Basic knowledge of DDD, Experience writing unit tests (xUnit or similar), Ability to work with partially documented systems and integrations, Hands-on experience using AI tools in development 📃 Skills: .NET, ASP.NET, EntityFramework, SQLServer, Redis, RabbitMQ, Docker, xUnit, Microservices, DDD, REST, AI 🏢 Description: About the project You’ll be working on backend systems within the energy and logistics domain , focusing on scalable platforms supporting services such as charging infrastructure, terminal operations, and logistics solutions. The systems are built using a modern microservices architecture , with strong emphasis on scalability, performance, and integrations. Duration: ~3 months (with possible extension) Your role Develop and maintain backend applications using .NET 8 Build and extend REST APIs ( ASP.NET Core) Support system architecture design (DDD, microservices) Work on integrations with internal systems Use RabbitMQ for communication between services Work with databases ( SQL Server, Redis ) Write unit tests ( xUnit ) Containerize applications using Docker Use AI tools in daily development (must-have) Collaborate with team members and support technical discussions Requirements 2.5–4+ years of experience as a .NET Developer Good knowledge of: .NET 8 ASP.NET Core API Entity Framework Core SQL Server Experience with: Redis RabbitMQ Docker Understanding of microservices architecture and DDD basics Experience writing tests ( xUnit or similar) Ability to work with partially documented systems and integrations Hands-on experience using AI tools in development (required) Nice to have Experience with complex integrations Experience in logistics / energy / enterprise systems Exposure to system design discussions What we offer Work on real, large-scale systems Flexible B2B cooperation Opportunity to grow into more senior/architectural responsibilities Possibility to extend cooperation after the initial contract Work environment where AI is part of daily development

🏢 Summary: The role involves developing and maintaining an enterprise-grade web application within the .NET ecosystem, with a strong focus on backend development and system architecture. You will design and enhance REST APIs, implement business logic, and integrate modern .NET Core solutions with legacy .NET Framework components. The position emphasizes scalable architecture, database optimization, and high code quality through comprehensive testing. 🗂️ Requirements: 5+ years of experience in .NET development, Strong expertise in .NET Core and backend systems, Experience designing and building REST APIs, Hands-on experience with Entity Framework Core, Experience with relational databases, especially SQL Server, Understanding of software architecture and design patterns, Experience working with .NET Framework 4.8, Experience with unit, integration, and end-to-end testing, Ability to integrate and maintain backend services, Basic knowledge of React or experience collaborating with frontend teams 📃 Skills: .NET, C#, ASP.NET, REST, Swagger, OpenAPI, EntityFramework, SQLServer, SQLite, React, xUnit, NUnit, AI, Copilot, ChatGPT 🏢 Description: Additional information The project focuses on the development and maintenance of an enterprise-grade web application built on the .NET ecosystem, with a strong emphasis on backend and system architecture. The main responsibility is to design and enhance REST APIs and business logic , including integration with existing components based on .NET Framework 4.8. The system relies on relational databases (SQL Server) and ORM solutions such as Entity Framework Core, with a strong focus on quality through multi-level testing. The role also involves collaboration with the frontend layer (React), although it is not the primary focus. The environment requires a high level of autonomy, technical decision-making, and a proactive approach to improving the existing architecture. You’re ideal for this role if you: Have 5+ years of experience in .NET development, with strong expertise in .NET Core and backend systems Are confident in designing and building REST APIs, including architecture and best practices (e.g., Swagger/OpenAPI) Have hands-on experience with Entity Framework Core and relational databases such as SQL Server Understand software architecture, design patterns, and how to build scalable, maintainable systems Are familiar with legacy environments, including .NET Framework 4.8, and can work across modern and existing solutions Have solid experience with testing (unit, integration, end-to-end) and care about code quality Have basic knowledge of React or are comfortable working closely with frontend teams Use AI tools (e.g., Copilot, ChatGPT) to improve development efficiency Take ownership of your work and proactively identify improvements rather than waiting for tasks Your day-to-day responsibilities include:​ Designing, developing, and maintaining backend services using .NET Core Building and enhancing REST APIs, ensuring performance, scalability, and clear documentation (Swagger/OpenAPI) Integrating new features with existing systems based on .NET Framework 4.8 Implementing business logic and ensuring consistency across application layers Working with databases (SQL Server, SQLite) and optimizing data access with Entity Framework Core Writing and maintaining tests (unit, integration, end-to-end) to ensure high code quality Collaborating with frontend developers (React) to ensure smooth end-to-end functionality Participating in architectural discussions and contributing to technical decisions Identifying areas for improvement and proactively proposing enhancements Using AI tools to streamline development and increase productivity

🏢 Summary: The offer is for a Back End Developer responsible for building and maintaining APIs, backend services, and scalable system architecture within the .NET ecosystem. The role focuses on designing microservices-based solutions, integrating databases and third-party services, and ensuring high performance, security, and reliability. It includes remote work options under a B2B contract. 🗂️ Requirements: Strong knowledge of backend technologies, especially .NET ecosystem, Experience with .NET 8+ and ASP.NET Core, Experience with relational databases (PostgreSQL or MySQL), Experience with NoSQL databases (MongoDB), Experience building RESTful APIs using Swagger / OpenAPI, Experience with Microservices Architecture, Experience with RabbitMQ for message queuing, Experience with Docker and Kubernetes, Experience with Auth0 and JWT-based authentication, Experience with cloud services (AWS, Azure or GCP) 📃 Skills: .NET, ASP.NET, C#, PostgreSQL, MySQL, MongoDB, REST, Swagger, OpenAPI, Microservices, RabbitMQ, Docker, Kubernetes, Auth0, JWT, AWS, Azure, GCP 🏢 Description: Description The Back End Developer will develop and maintain APIs, services, and server-side logic and databases. You'll contribute to system architecture and help scale our platforms. You will ensure high performance and responsiveness of applications, working alongside frontend developers and other team members. Responsibilities Design, build and implement backend services and APIs Design data models and manage database integration Integrate with databases and third-party APIs Implement security and data protection measures Optimize performance and security of systems Requirements Strong knowledge of backend technologies / languages, particularly .NET ecosystem Experience in .NET 8+ (or latest version), including ASP.NET Core for building web APIs and services. Experience with relational databases, such as PostgreSQL, MySQL for structured data, complex queries, and ACID compliant operations Experience with NoSQL databases, such as MongoDB, for handling unstructured or semi-structured data, schema flexibility, and high-throughput scenarios Experience with RESTful APIs for development of robust, secure RESTful services with best practice for APU design, versioning and documentation, using Swagger / Open API Experience in Microservices Architecture, for design, implementation, and management of distributed systems using microservices principles, ensuring loose coupling, scalability, and resilience Experience in Message Queuing:, using RabbitMQ for asynchronous communication, event-driven architecture, and reliable message brokering between services Experience in Containerization and Orchestration, using Kubernetes (K8s) for deploying, scaling, and managing containerized applications in production environments and Docker for containerization Experience in Authentication, using Auth0 for identity management, JWT-based authentication Experience in Cloud Services, such as AQS, Azure, GC Nice to have Experience in Rabbit MQ Middleware Prior experience in the EdTech domain (e-learning platforms, digital classrooms, LMS) Knowledge of learning science, instructional design, or accessibility standards (e.g., WCAG) Familiarity with tools like Moodle, Canvas, Zoom SDK, or Google Classroom integration Working conditions Partly / fully remote B2B contract

🏢 Summary: Offer for a .NET Backend Developer focused on building backend services in a microservices and cloud-native environment. The role includes developing REST APIs, API-to-API integrations, data access layers, and collaborating in Scrum teams using modern backend technologies. 🗂️ Requirements: Experience as .NET Backend Developer, Practical knowledge of .NET, Knowledge of Scrum, Practical knowledge of Git, Experience with API-to-API communication, Knowledge of asynchronous programming, Experience designing and implementing REST API, Practical knowledge of Entity Framework, Good knowledge of SQL, Experience with PostgreSQL, Experience with microservices architecture, Knowledge of Cloud Native solutions 📃 Skills: .NET, Scrum, Git, REST, EntityFramework, SQL, PostgreSQL, Microservices, CloudNative, Async, API, AWS, Kubernetes, KQL, SIEM, Elastic, Hangfire, gRPC, GraphQL 🏢 Description: O projekcie Poszukujemy .NET Backend Developera do realizacji projektów opartych o architekturę mikroserwisową i rozwiązania cloud-native. Rola obejmuje rozwój usług backendowych, integrację systemów poprzez API oraz współpracę z zespołem projektowym zgodnie z metodyką Scrum. Twój zakres obowiązków projektowanie i rozwój aplikacji backendowych w technologii .NET implementacja oraz rozwój mikroserwisów tworzenie i rozwój REST API integracja systemów z wykorzystaniem komunikacji API-to-API projektowanie i rozwój rozwiązań opartych o architekturę cloud-native współpraca z zespołem projektowym w metodyce Scrum rozwój oraz utrzymanie warstwy dostępu do danych udział w przeglądach kodu oraz stosowanie dobrych praktyk programistycznych Nasze wymagania doświadczenie jako .NET Backend Developer praktyczna znajomość .NET znajomość metodyki Scrum praktyczna znajomość Git doświadczenie w komunikacji API-to-API znajomość programowania asynchronicznego (Async) doświadczenie w projektowaniu i implementacji REST API praktyczna znajomość Entity Framework dobra znajomość SQL doświadczenie z PostgreSQL doświadczenie w pracy z architekturą mikroserwisową znajomość rozwiązań Cloud Native Mile widziane znajomość AWS doświadczenie z Kubernetes znajomość KQL doświadczenie z SIEM znajomość Elastic znajomość Hangfire doświadczenie z gRPC znajomość GraphQL

🏢 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: Offer for a senior fullstack developer role focused on building and developing backend applications in .NET and frontend solutions in React within a microservices architecture. The position involves working with SQL Server, Cosmos DB, Azure services, REST APIs, and Micro Frontends, with strong emphasis on code quality, scalability, and performance. The role requires close collaboration with product and architecture teams. 🗂️ Requirements: Very good knowledge of .NET, Very good knowledge of React, Experience with SQL Server, Experience with Cosmos DB, Practical experience with Azure, Experience with Azure Functions, Experience in designing and integrating REST API, Knowledge of microservices architecture, Experience in Micro Frontend development, Minimum 5 years of commercial experience in similar role 📃 Skills: .NET, React, SQL, SQLServer, CosmosDB, Azure, AzureFunctions, REST, Microservices, MicroFrontends 🏢 Description: Zakres obowiązków: Projektowanie i rozwój aplikacji backendowych w technologii .NET Tworzenie i rozwijanie interfejsów użytkownika w React Praca z bazami danych SQL Server oraz Cosmos DB Projektowanie i implementacja API REST Rozwój rozwiązań opartych o architekturę mikroserwisową Tworzenie i utrzymanie Azure Functions Praca nad rozwiązaniami typu Micro Frontends (MFE) Współpraca z zespołami produktowymi i architektonicznymi Dbanie o jakość kodu, wydajność i skalowalność rozwiązań Wymagania techniczne: Bardzo dobra znajomość .NET Bardzo dobra znajomość React Doświadczenie w pracy z SQL Server i Cosmos DB Praktyczna znajomość Azure (w szczególności Azure Functions) Doświadczenie w projektowaniu i integracji REST API Znajomość architektury mikroserwisowej Doświadczenie w Micro Frontend (MFE) development Minimum 5 lat doświadczenia komercyjnego na podobnym stanowisku

🏢 Summary: Development of backend applications using .NET/.NET Core in a banking environment, including building REST APIs, business logic modules, and system integrations. The role involves working in AWS to deploy serverless and containerized services, managing SQL databases, and ensuring security and regulatory compliance. Close collaboration with business teams is required to deliver high-quality, secure financial solutions. 🗂️ Requirements: Minimum 6 years of experience as .NET Developer, Strong knowledge of .NET and C#, Hands-on experience with AWS services (Lambda, ECS/EKS, S3, RDS), Experience with REST API development, Proficiency in Kafka, Proficiency in SQL and database design, Experience with containerization, Experience in banking or financial projects, Understanding of security and regulatory requirements, Very good English skills 📃 Skills: .NET, C#, AWS, Lambda, ECS, EKS, S3, RDS, Kafka, SQL, REST, Docker, Kubernetes 🏢 Description: Scope of Responsibilities: Design and development of backend applications based on .NET / .NET Core. Creation and maintenance of REST APIs, integrations, and business logic modules. Working in an AWS environment – building and deploying serverless services, containerization, and process automation. Working with SQL databases (data model design, query optimization). Collaboration with analysts and business teams within the banking domain. Ensuring code quality, application security, and compliance with financial sector regulatory requirements. Requirements: Minimum 6 years of experience as a .NET Developer. Strong knowledge of .NET / .NET Core (C#). Hands-on experience with AWS (Lambda, ECS/EKS, S3, RDS, or other services). Proficiency in Kafka and SQL. Experience in banking or financial projects (knowledge of regulatory processes, security, and system integrations is a plus). Very good command of English (daily communication).

🏢 Summary: Backend Developer (.NET) role focused on development, maintenance, and modernization of an existing logistics system. The position involves working with legacy code, fixing bugs, refactoring, and improving business logic within a live operational environment. The role requires close collaboration with development and analytics teams. 🗂️ Requirements: 3–5 years of experience with .NET, Proficiency in C#, Experience with ASP.NET MVC or ASP.NET Core, Strong knowledge of SQL Server, Experience working with legacy codebases, Ability to debug and analyze complex issues, Experience with REST API, English level B2 minimum 📃 Skills: .NET, C#, ASP.NET, MVC, Core, SQL, SQLServer, REST, EntityFramework, Docker, UnitTesting 🏢 Description: Organizacja z branży logistycznej, rozwijająca własne systemy operacyjne, poszukuje osoby na stanowisko Backend Developer (.NET). Rola skupiona jest na rozwoju i stabilizacji istniejącego systemu oraz stopniowym jego unowocześnianiu. Zakres obowiązków Rozwój i utrzymanie systemu w technologii .NET Analiza i rozwiązywanie błędów w systemie (bugfixy) Refaktoryzacja istniejącego kodu Analiza logiki biznesowej i jej usprawnianie Współpraca z zespołem developerskim i analitycznym Praca z kodem bez pełnej dokumentacji Wymagania Min. 3–5 lat doświadczenia w .NET Dobra znajomość: C# ASP.NET (MVC / Core) SQL Server Doświadczenie w pracy z istniejącym kodem (legacy) Umiejętność debugowania i analizy problemów Znajomość REST API Znajomość języka angielskiego na poziomie minimum B2 Mile widziane Entity Framework (klasyczny i Core) Podstawy testów jednostkowych Znajomość Docker Oferujemy Pracę przy systemach o realnym wpływie na operacje biznesowe Możliwość rozwoju technologicznego Stabilne zatrudnienie Wpływ na jakość i rozwój systemu

🏢 Summary: The offer is for a Senior .NET Developer responsible for improving and refactoring core backend systems to enhance structure, maintainability, and security. The role focuses on reducing technical debt, enabling automation and AI integration, and ensuring high code quality through testing and CI/CD practices. The position involves hands-on development within legacy or monolithic environments and driving system modernization. 🗂️ Requirements: 5+ years experience in .NET / C# backend development, Experience with legacy or monolithic systems, Strong knowledge of clean code principles, Proven experience in refactoring existing codebases, Strong SQL and backend integration experience, Experience with APIs and service-based architecture, Experience with CI/CD pipelines, Experience with automated testing, Familiarity with TDD or BDD practices, Experience with Gherkin, SpecFlow, Cucumber or similar, Experience using AI tools in development workflows, Understanding of code structuring for automation and AI integration 📃 Skills: .NET, C#, SQL, APIs, CI/CD, TDD, BDD, Gherkin, SpecFlow, Cucumber, AI, Git, Docker, .NETCore 🏢 Description: Introduction & Summary: We are seeking a Senior .NET Developer with 5-8+ years of experience in backend development and .NET engineering. The successful candidate will drive improvement in code quality, reduce technical debt, and support system structuring for better predictability. With a focus on future automation and AI capabilities, you will help ensure code understandability, maintainability, and security. Main Responsibilities: Responsible for hands-on development and refactoring of core systems, with the aim of enhancing their structure and predictability. Develop and improve .NET-based systems. Reduce technical debt and increase maintainability. Support safe and efficient delivery. Ensure code is understandable, maintainable, and secure. Make systems testable and observable. Facilitate automation of workflows. Key Requirements: Strong experience with .NET / C#. Experience working with legacy or monolithic systems. Strong understanding of clean code principles. Experience with refactoring and improving existing codebases. Strong SQL and backend integration experience. Experience with APIs and service-based architecture. Experience with CI/CD pipelines. Experience with automated testing. Familiarity with TDD / BDD and security by design thinking. Experience with Gherkin / SpecFlow / Cucumber or similar. AI-related: Experience using AI tools in development workflows. Understanding of code structuring for automation and AI integration. Experience using AI for debugging, testing, or documentation support. Nice to Have: Experience with .NET Core. Experience with containerization. Exposure to AI-assisted testing or development tools. Experience improving system observability.

🏢 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.