Senior .NET Developer

🏢 Summary: Senior .NET Developer role focused on building and enhancing a cloud-native embedded finance platform in a regulated FinTech environment. The position involves designing, developing, and deploying scalable, secure features using a modern tech stack while ensuring high performance and reliability in production. You will work across backend and frontend technologies, contributing to CI/CD, cloud infrastructure, and event-driven systems. 🗂️ Requirements: 5+ years of software development experience, Strong OOP and system design skills, Hands-on experience with .NET and C#, Hands-on experience with Angular, Understanding of software testing concepts, Experience with cloud-native architectures, Experience with CI/CD and DevOps practices, Experience with relational databases, Experience with NoSQL databases, Knowledge of performance, security, and availability principles, Experience in FinTech, payments, banking, or regulated environments, Upper-Intermediate English or higher 📃 Skills: C#, .NET, Angular, AWS, CI/CD, Docker, Kubernetes, Kafka, RabbitMQ, Datadog, SQL, NoSQL, OOP, DDD 🏢 Description: Looking to take your .NET expertise to the next level while working on high-impact FinTech solutions? This role offers the chance to contribute to scalable, cloud-native systems that empower thousands of businesses worldwide. We’re seeking a Senior .NET Developer to join our team, collaborating with talented engineers, product managers, and designers to deliver innovative financial technology. At Sigma Software, we work with some of the most forward-thinking companies in the industry. This opportunity will let you grow professionally while making a tangible difference in a fast-paced, regulated environment. Customer Our customer is a leading FinTech company providing embedded financing solutions for platforms and marketplaces. Their mission is to enable businesses to offer flexible credit products to customers, helping SMEs access funding quickly and efficiently. The customer is recognized for innovation in embedded finance, serving thousands of businesses globally and partnering with major platforms. They operate in a regulated environment with a strong focus on scalability, performance, and security. Project The project involves enhancing and expanding customer’s embedded finance platform, which integrates directly into partner services to deliver fast, flexible funding to SMEs. You’ll work on a modern tech stack, building features that improve customer and partner experiences while ensuring reliability in production. Key Technologies: C#, .NET Core, Angular 18, AWS, CI/CD, Docker/Kubernetes, Kafka/RabbitMQ, Datadog, relational & NoSQL databases. Responsibilities Design, build, and deliver features and projects across C#, .NET Core, and Angular stack Write clean, maintainable, and well-tested code (unit/integration/e2e) Take ownership of features from requirements breakdown to deployment Deploy and monitor services in AWS cloud-native environments Handle production issues and incidents with accountability Collaborate with Product, Design, and Engineering teams in Agile practices Contribute to continuous improvement of systems and processes Requirements 5+ years of experience in software development with strong OOP and system design skills Solid hands-on experience with .NET (C#) and Angular Understanding of software testing concepts and practices Expertise in cloud-native and DevOps practices (CI/CD, automation, monitoring) Experience with relational and NoSQL databases Knowledge of non-functional requirements (performance, security, availability) Proven experience in FinTech, payments, banking, or regulated financial environments Upper-Intermediate English level or higher Will be a plus Experience with Docker/Kubernetes Familiarity with event-driven architectures (Kafka, RabbitMQ) Proficiency with observability tools (Datadog or similar) Knowledge of domain-driven design (DDD) and complex domain modeling Personal profile Growth mindset, curiosity, and proactivity Strong problem-solving skills balancing complexity and simplicity Feedback-oriented, open to giving and receiving constructive input Ownership & accountability in delivering commitments Team player with strong collaboration skills Adaptability to changing priorities Excellent communication skills across disciplines

🏢 Summary: Senior C#/.NET Developer role focused on building and scaling high-performance backend systems for risk management, XVA, and asset-liability management within the financial domain. The position involves modernizing legacy components into a scalable, event-driven architecture and working across the full software development lifecycle in an agile, distributed team. Strong expertise in distributed systems, DevOps practices, and capital markets risk concepts is required. 🗂️ Requirements: 5+ years enterprise experience with C# and .NET (Web API, asynchronous programming, background services), Strong knowledge of distributed systems and Enterprise Integration Patterns, Experience with message brokers/service buses (e.g., RabbitMQ, MassTransit, Rebus), Solid experience with MS SQL Server or other relational databases, Experience with micro-ORMs (e.g., Dapper), Proficiency with Git-based repositories and CI/CD platforms (Jenkins, TeamCity, GitLab CI), Experience with configuration management tools (e.g., Ansible), Practical exposure to Generative AI / Agentic AI workflows in software engineering, Strong understanding of Capital Markets and derivatives (Listed and OTC), Knowledge of risk management concepts (Greeks, PnL Explain), Understanding of Valuation Adjustments (CVA, FVA) and liquidity/balance sheet metrics 📃 Skills: C#, .NET, ASP.NET, WebAPI, SignalR, RabbitMQ, MassTransit, Rebus, MSQL, Dapper, Git, Bitbucket, Jenkins, TeamCity, Ansible, CI/CD, SQL, XVA, ALM 🏢 Description: We are looking for a Senior C#/.NET Developer with Financial Domain Knowledge. In this role, you will be responsible for designing and scaling high-performance backend systems that support advanced risk management, valuation adjustments (XVA), and asset-liability management (ALM). You will work within a distributed, agile engineering team focused on modernizing legacy components into a highly scalable, event-driven architecture. Key Responsibilities Designing and developing high-performance C#/.NET applications and backend services Building scalable, event-driven and distributed systems in enterprise environments Developing asynchronous communication solutions using messaging frameworks (e.g. Rebus) Working with ASP.NET Web API, Windows Services, and SignalR Applying clean architecture, SOLID principles, and design patterns in daily development Collaborating in Agile teams across international environments Participating in full software development lifecycle, including architecture, implementation, testing, and deployment Working with CI/CD pipelines and DevOps tools such as Git, Bitbucket, Jenkins, TeamCity, and Ansible Optimizing and maintaining MS SQL databases and data-intensive applications Using ORM tools such as Dapper for efficient data access Contributing to code reviews, technical improvements, and engineering best practices Leveraging LLMs and AI-assisted development tools to improve software quality and engineering efficiency Delivering maintainable, scalable, and well-documented solutions under tight deadlines Requirements 5+ years of hands-on experience in enterprise-level software development using C# and the .NET ecosystem (including Web API, asynchronous programming, and background services). Strong command of System Architecture: practical knowledge of distributed systems, Enterprise Integration Patterns, and message brokers/service buses (e.g., RabbitMQ, MassTransit, Rebus or similar). Solid database experience with MS SQL Server (or other relational databases) and micro-ORMs (e.g., Dapper) optimized for high throughput. Proficiency with standard DevOps toolchains: Git-based repositories, modern CI/CD platforms (Jenkins/TeamCity/GitLab CI), and configuration management tools. Practical exposure to Generative AI / Agentic AI workflows applied to software engineering practices. Financial Domain Knowledge (Quantitative & Risk) Solid understanding of Capital Markets, including Listed and OTC derivatives. Familiarity with risk management concepts: Greeks (Delta, Gamma, Vega, Theta) and PnL Explain. Understanding of Valuation Adjustments (XVA) such as CVA, FVA. General awareness of Liquidity Risk, Balance Sheet Metrics, and transactional workflows (pre-trade/booking).

🏢 Summary: Senior .NET Developer role focused on building and maintaining secure, high-performance online banking solutions in a distributed Agile environment. The position involves developing backend features in .NET 8, optimizing SQL-based data access, and working with containerized applications. Hybrid work model with strong emphasis on reliability, security, and collaboration. 🗂️ Requirements: Minimum 4 years of experience in IT system development, Hands-on experience with .NET, especially .NET 8, Strong knowledge of PostgreSQL, Strong knowledge of MS SQL, Experience with Docker, Experience with Kubernetes, Practical experience in Agile software development, Experience in developing new features and maintaining existing systems, Good command of Polish, Legal right to work in the European Union 📃 Skills: .NET, C#, PostgreSQL, MSSQL, SQL, Docker, Kubernetes, Agile 🏢 Description: Ignite digital innovation — shape the future of online banking! Warszawa-based opportunity with hybrid work model (2 days in the office/month, up to 4 remote days/week). As a Senior .NET Developer , you will be working for our client, a leader in online banking, supporting the development and maintenance of secure, high-performance financial solutions. You’ll join a dynamic team dedicated to building cutting-edge banking functionalities, ensuring top-tier reliability and innovation. Operating within a distributed Agile environment, you’ll play a pivotal role in implementing complex backend logic while collaborating seamlessly across teams. This is your chance to contribute to transformative financial technology and accelerate your career growth. Your main responsibilities: Design and develop new features in .NET 8 to enhance banking solutions. Implement and optimize SQL-based data access for performance and security. Build and maintain containerized applications using Docker and Kubernetes. Collaborate with distributed teams within an Agile framework. Participate in the development of secure payment solutions. Share knowledge and mentor less experienced team members. Ensure code quality through reviews and testing. Maintain existing functionalities and address production issues. Manage your time effectively while working remotely. You're ideal for this role if you have: At least 4 years of experience in IT system development. Solid hands-on experience with .NET (especially .NET 8). Strong knowledge of PostgreSQL and MS SQL. Practical understanding of Agile software development. Excellent communication and collaboration skills in distributed teams. Ability to work independently and manage your responsibilities. Experience developing new features and maintaining existing ones. Passion for software development and continuous learning. Experience with Docker and Kubernetes. It is a strong plus if you have: (optional) Certifications in relevant technologies. Experience with financial or payment systems. Language Required for the role: Good command of Polish. Eligibility to work on this role: Only candidates with an existing legal right to work in the European Union will be considered for this role. #MAKEYourCareerBETTER Interested? Apply now and include your CV (preferably in English) along with a statement confirming your consent to the processing and storage of your personal data.

🏢 Summary: Senior .NET Developer role focused on designing, extending, and modernising critical banking and securities systems in a fully remote B2B model. The position involves full-stack development, system integration, and cloud scaling within distributed, business-critical environments. The role requires close collaboration with business stakeholders and ownership of end-to-end application delivery. 🗂️ Requirements: 5+ years experience as .NET / C# Developer, Experience in banking or investment banking sector, Full-stack development experience, Knowledge of SOLID design principles, Experience with document-based databases, Experience with event-driven messaging frameworks, Experience with unit and integration testing, End-to-end application development experience, Ability to work during UK business hours, Based in Poland 📃 Skills: .NET, C#, MongoDB, SOLID, Messaging, UnitTesting, IntegrationTesting, Docker, Kubernetes, Cloud 🏢 Description: Work model: 100% remote (candidates must be based in Poland) Contract type: B2B Industry: Banking / Investment Banking We are looking for an experienced Senior .NET Developer to join a distributed engineering team working on critical banking systems. The role focuses on extending and modernising applications used across securities and banking operations, with a strong emphasis on system design, scalability, and cloud transformation. You will work end-to-end on business-critical systems, closely collaborating with Business Analysts, without a separate QA team. A solid background in banking or financial services is essential. Main Responsibilities: Design, develop, and extend .NET-based systems supporting multiple banking entities Contribute to the integration of securities and core banking platforms Support and enhance a portfolio of ~17 applications across product control and risk management Work with an in-house development framework in a full-stack capacity Participate in scaling applications for cloud-based, containerized environments Collaborate closely with business stakeholders to deliver robust solutions Ensure high code quality through unit and integration testing Key Requirements: 5+ years of professional experience as a .NET / C# Developer Hands-on experience in the banking or investment banking sector (mandatory) Full-stack development experience (backend-focused, frontend included) Strong understanding and practical application of SOLID design principles Experience with document-based databases (e.g. MongoDB) Experience with event-driven / event-based messaging frameworks Solid knowledge of unit and integration testing Experience working end-to-end on applications (development, testing, support) Ability to work independently in a fast-paced, regulated environment Availability during UK business hours Nice to Have: Experience with cloud platforms and application migration to cloud Experience with container technologies (e.g. Docker, Kubernetes) Exposure to systems such as Murex or large in-house banking platforms Background in securities, risk, or product control systems Other Details: This role is 100% remote with candidates required to be located in Poland. The contract is on a B2B basis within the banking and investment banking industry.

🏢 Summary: Senior .NET Developer role focused on designing, extending, and modernizing critical banking systems within securities and core banking domains. The position involves full-stack development, system integration, and cloud scaling in a distributed team without a separate QA function. Work includes end-to-end ownership of business-critical applications in a regulated investment banking environment. 🗂️ Requirements: 5+ years experience with .NET and C#, Hands-on experience in banking or investment banking, Full-stack development experience, Strong knowledge of SOLID principles, Experience with document-based databases, Experience with event-driven messaging frameworks, Knowledge of unit and integration testing, End-to-end application development experience, Ability to work independently in regulated environments, Availability during UK business hours, Poland-based residency 📃 Skills: .NET, C#, MongoDB, SQL, REST, Microservices, Docker, Kubernetes, Azure, UnitTesting, IntegrationTesting, EventDriven, Git 🏢 Description: Work model: 100% remote (candidates must be based in Poland) Contract type: B2B Industry: Banking / Investment Banking We are looking for an experienced Senior .NET Developer to join a distributed engineering team working on critical banking systems. The role focuses on extending and modernising applications used across securities and banking operations, with a strong emphasis on system design, scalability, and cloud transformation. You will work end-to-end on business-critical systems, closely collaborating with Business Analysts, without a separate QA team. A solid background in banking or financial services is essential. Main Responsibilities: Design, develop, and extend .NET-based systems supporting multiple banking entities Contribute to the integration of securities and core banking platforms Support and enhance a portfolio of ~17 applications across product control and risk management Work with an in-house development framework in a full-stack capacity Participate in scaling applications for cloud-based, containerized environments Collaborate closely with business stakeholders to deliver robust solutions Ensure high code quality through unit and integration testing Key Requirements: 5+ years of professional experience as a .NET / C# Developer Hands-on experience in the banking or investment banking sector (mandatory) Full-stack development experience (backend-focused, frontend included) Strong understanding and practical application of SOLID design principles Experience with document-based databases (e.g. MongoDB) Experience with event-driven / event-based messaging frameworks Solid knowledge of unit and integration testing Experience working end-to-end on applications (development, testing, support) Ability to work independently in a fast-paced, regulated environment Availability during UK business hours Nice to Have: Experience with cloud platforms and application migration to cloud Experience with container technologies (e.g. Docker, Kubernetes) Exposure to systems such as Murex or large in-house banking platforms Background in securities, risk, or product control systems Other Details: This role is 100% remote with candidates required to be located in Poland. The contract is on a B2B basis within the banking and investment banking industry.

🏢 Summary: Senior .NET Developer role focused on building and maintaining secure, high-performance online banking solutions in a hybrid work model. The position involves developing new backend features, optimizing databases, and managing containerized applications in an Agile, distributed environment. The role also includes ensuring code quality, supporting production systems, and contributing to secure payment functionalities. 🗂️ Requirements: Minimum 4 years of experience in IT systems development, Strong hands-on experience with .NET, Strong knowledge of PostgreSQL, Strong knowledge of MS SQL, Experience with Docker, Experience with Kubernetes, Practical understanding of Agile methodology, Ability to develop new features and maintain existing systems, Ability to work independently in distributed teams 📃 Skills: .NET, C#, PostgreSQL, MS SQL, SQL, Docker, Kubernetes, Agile, Elixir, Sorbnet 🏢 Description: Innovate online banking and join the team as a Senior .NET Developer! Warsaw-based opportunity with hybrid work model (2 times in the office/month). As a Senior .NET Developer , you will be working for our client, one of the leaders in online banking, supporting the development and maintenance of secure, high-performance financial solutions. You’ll be contributing to a team responsible for building and enhancing banking functionalities, ensuring reliability and innovation. Working in a distributed Agile environment, you’ll play a key role in both implementing complex backend logic and actively collaborating with cross-functional teams. Your main responsibilities: Design and develop new features in .NET 8 Implement and optimize SQL-based data access Build and maintain containerized applications using Docker and Kubernetes Collaborate with distributed teams in an Agile environment Participate in the development of secure payment solutions Share knowledge and support less experienced team members Ensure code quality through code reviews and testing Maintain existing functionalities and resolve production issues Manage your own time and responsibilities while working remotely You're ideal for this role if you have: Strong experience in developing IT systems (min. 4 years of experience) Solid hands-on experience with .NET Strong knowledge of PostgreSQL and MS SQL Practical understanding of Agile software development Excellent communication and collaboration skills in distributed teams Ability to work independently and manage your time effectively Experience in developing new features and maintaining existing ones A passion for software development and continuous learning Experience with Docker and Kubernetes Nice to have: Knowledge of banking domain such as payments and transactions (e.g. Elixir, Sorbnet)

🏢 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: Senior .NET Developer role focused on designing, developing, and maintaining critical backend applications within a secure, large-scale financial enterprise environment. The position involves contributing to architectural decisions and delivering robust solutions that support complex financial operations. Ideal for a senior engineer seeking technical autonomy and impact in a stable yet modern setting. 🗂️ Requirements: Senior-level experience in .NET development, Proven experience designing backend applications, Experience developing and maintaining enterprise-grade systems, Ability to contribute to software architecture and technical design, Experience working in secure, large-scale environments, Strong understanding of robust engineering practices 📃 Skills: .NET, C#, Backend, Architecture, Enterprise, FinancialSystems 🏢 Description: Are you a seasoned software engineer looking to drive impactful backend solutions within a secure, large-scale enterprise environment? A leading international financial institution is seeking a Senior .NET Developer to join a highly specialized engineering team. In this role, you will play a pivotal part in designing, developing, and maintaining critical applications that support sophisticated financial operations. This is an exceptional opportunity for a senior professional who thrives on technical autonomy, values robust engineering practices, and is looking for a stable yet modern environment where their architectural input truly matters.

🏢 Summary: Senior .NET Developer role focused on building and enhancing distributed microservices for digital banking systems in a European financial environment. The position involves designing scalable, high-quality solutions using C# and .NET, implementing asynchronous communication, and ensuring robust automated testing practices. Remote-first model with collaboration on complex financial platforms. 🗂️ Requirements: 5+ years of experience in C# and .NET development, Strong experience with microservices architecture, Knowledge of CQRS, REST, OOP, EventSourcing, Experience with RabbitMQ or Kafka, Experience with NoSQL and relational databases, Experience with automated testing (unit, integration, contract), Knowledge of DomainDrivenDesign principles, Understanding of BPMS workflows, Experience with Git, Good command of Polish, Legal right to work in the EU 📃 Skills: C#, .NET, Microservices, CQRS, REST, OOP, EventSourcing, RabbitMQ, Kafka, Git, NoSQL, SQL, Docker, Testcontainers, Pact, DomainDrivenDesign, BPMS 🏢 Description: Unleash innovation — revolutionize financial systems with expert .NET development! Wroclaw-based opportunity with remote work model (5 remote days per week). As a Senior .NET Developer , you will be working for our client, a leading financial organization committed to transforming the digital banking experience. You’ll contribute to building and enhancing distributed microservices that enable seamless financial operations across Europe, driving innovation and operational excellence. Your main responsibilities: Develop and maintain scalable, high-quality microservices using C# and .NET technologies following Domain-Driven Design principles. Design and implement asynchronous communication patterns with RabbitMQ or Kafka to ensure system robustness. Collaborate with cross-functional teams to create automated tests, including unit, integration, and contract tests, utilizing Docker, Testcontainers, and Pact. Optimize code for performance, scalability, and reliability, adhering to Clean Code standards. Implement RESTful APIs and work with NoSQL and relational databases for effective data management. Contribute to the continuous improvement of development processes and best practices. Engage proactively in team collaboration, sharing knowledge and solving complex technical challenges. You're ideal for this role if you have: Minimum of 5 years of experience in C# and .NET development in a senior role. Understanding of workflows in BPMS platforms. Strong knowledge of microservices architecture, CQRS, REST, OOP, and Event Sourcing. Practical experience with asynchronous messaging (RabbitMQ/Kafka), Git, NoSQL databases, and relational databases. Familiarity with automated testing frameworks, including unit, integration, and contract testing. Good understanding of Domain-Driven Design (DDD) principles and clean code practices. Excellent team collaboration skills and a responsible, engaged work attitude. It is a strong plus if you have: Experience with Polish language communication skills. Knowledge of automated testing tools and frameworks. Language Required for the role: Polish: Good command Eligibility for the role: Only candidates with an existing legal right to work in the European Union will be considered for this role. #MAKEYourCareerBETTER Interested? Apply now and include your CV (preferably in English) along with a statement confirming your consent to the processing and storage of your personal data.

🏢 Summary: Long-term project for a Senior/Expert .NET Developer focused on backend and API development within enterprise banking systems. The role involves developing and optimizing software solutions, working with legacy code, and providing technical leadership and mentorship. The position emphasizes high-quality standards, collaboration, and code excellence in a complex financial environment. 🗂️ Requirements: Strong knowledge of C#, Strong knowledge of .NET framework, Expertise in ASP.NET Core, Experience in API development, Experience with SQL Server design and development, Ability to analyze and troubleshoot legacy code, Solid understanding of OOP principles, Knowledge of software engineering best practices 📃 Skills: C#, .NET, ASP.NET, SQL, T-SQL, Git, Jenkins, Angular, HTML, CSS, JavaScript, Visual Studio, Postman, Swagger, Bitbucket, Bootstrap, SQL Server 🏢 Description: We’re looking for an Expert/Senior .NET Developer to join a long-term project for a leading client in the banking industry. Project Type: Enterprise banking systems – backend & API development, code optimization, and mentorship Responsibilities: Design, develop, and maintain software solutions Analyze, refactor, and troubleshoot legacy code Conduct code reviews and uphold high-quality standards Collaborate with QA and Business Analysts Mentor junior developers and provide technical leadership Must-Have Experience: Strong knowledge of C# and the .NET framework Expertise in ASP.NET Core and API development Experience with SQL Server (design & development) Ability to work with and troubleshoot legacy code Solid understanding of OOP and software engineering best practices Nice-to-Have: Familiarity with Git, Jenkins, and testing frameworks Understanding of cloud concepts & web security best practices Knowledge of frontend technologies (Angular, HTML, CSS, JavaScript) Tools & Tech Stack:Visual Studio, Postman, Swagger, Bitbucket, SQL Server Management Studio, T-SQL, Bootstrap (or similar)