[Job-32156] Senior .NET Backend Developer

At CI&T, we help large enterprises transform the potential of AI into real business impact with AI Deployment, AI-native execution, and tech-integrated business solutions. With 30 years of experience in technological transformation, we accelerate innovation with expertise in Agentic SDLC, Application modernization, Data & AI, Martech and Business strategy. We are 8,000 CI&Ters across more than 25 countries, collaborating to build solutions with real impact. AI is already part of how we work, evolve, and innovate every day. At CI&T, we are looking for a skilled and motivated Senior .NET Backend Developer to join one of our delivery teams. You will design, build and evolve scalable, secure and maintainable backend services using a modern .NET stack, working closely with Product, Architecture, QA and Frontend colleagues in a collaborative, multicultural and fast-moving environment. Your responsibilities Design, develop and maintain RESTful APIs and backend services using C# and .NET 8+. Apply Clean Architecture, SOLID and KISS principles to keep code modular, reusable and simple. Build event-driven and asynchronous integrations using messaging platforms such as Azure Service Bus, RabbitMQ or Kafka. Model, query and optimize relational databases such as PostgreSQL and SQL Server, using Entity Framework Core. Work with document databases such as MongoDB, when needed. Implement secure authentication and authorization using OAuth2/OIDC and JWT. Write and maintain automated unit and integration tests using tools such as xUnit, NSubstitute and Bogus. Contribute to CI/CD pipelines, including Azure DevOps and YAML pipelines, and follow agreed branching strategies such as GitFlow. Instrument services for observability, including structured logging, metrics and tracing, and help diagnose production issues. Critically read, validate and review code, including code generated by AI tools, to uphold quality, security and performance standards. Take part in code reviews, technical refinement and estimation, and help mentor less experienced developers. Work with technical and non-technical stakeholders to turn requirements into pragmatic, maintainable solutions. Requirements for this challenge Solid experience as a backend developer working with C# and .NET, ideally .NET 8+, including production-grade RESTful APIs. Strong knowledge of object-oriented design, SOLID principles, design patterns and Clean Architecture. Hands-on experience with MediatR, AutoMapper and Entity Framework Core. Experience with relational databases such as PostgreSQL or SQL Server, including data modelling and query optimization. Experience with distributed systems and messaging, using technologies such as Azure Service Bus, Rebus, RabbitMQ, Kafka or equivalent. Practical use of AI tools in software development, such as GitHub Copilot, Claude, OpenAI APIs or similar, including AI-assisted code generation, testing and refactoring. Experience building autonomous or semi-autonomous agents for software development, or knowledge of prompt engineering and evaluating AI output quality. Experience with automated testing, including unit and integration testing and the use of test doubles. Working knowledge of Docker and Docker Compose. Familiarity with observability tools such as Datadog, Grafana, Application Insights or the ELK Stack. Experience with Git, CI/CD pipelines and Azure DevOps, or similar tools. Good communication skills and a collaborative, ownership-driven mindset. Good spoken and written English (upper-intermediate or above). Nice to have Knowledge of CQRS and Domain-Driven Design (DDD). Experience with MongoDB, including document modelling and aggregation. Knowledge of Infrastructure as Code, using technologies such as Terraform, Bicep or ARM. Exposure to a frontend framework such as React, Angular or Vue, including API integration from the client side. Experience working in polyglot environments, such as Node.js, Python or Java. #midsenior #Li-MG04 Our benefits: Health and dental insurance Meal and food allowance Childcare assistance Extended paternity leave Partnership with gyms and health and wellness professionals via Wellhub (Gympass) TotalPass; Profit Sharing and Results Participation (PLR); Life insurance Continuous learning platform (CI&T University); Discount club Free online platform dedicated to physical, mental, and overall well-being Pregnancy and responsible parenting course Partnerships with online learning platforms Language learning platform And many more! More details about our benefits here: https://ciandt.com/br/pt-br/carreiras At CI&T, inclusion starts at the first contact. If you are a person with a disability, it is important to present your assessment during the selection process. See which data needs to be included in the report by clicking here.This way, we can ensure the support and accommodations that you deserve. If you do not yet have the assessment, don't worry: we can support you in obtaining it. We have a dedicated Health and Well-being team, inclusion specialists, and affinity groups who will be with you at every stage. Count on us to make this journey side by side.