[Job-32277] Senior FullStack Developer (.NET/Javascript/React)

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.

Job Overview:

We are on the lookout for a passionate and experienced Senior Fullstack Developer to join our engineering team. The ideal candidate will have a strong background in web application development—specifically with .NET Core—and the flexibility and eagerness to adapt to and learn new technologies, including legacy ASP.NET and modern JavaScript frameworks. Additionally, a solid understanding of frontend engineering using React is essential to build, maintain, and evolve high-performance user interfaces.

Key Responsibilities:
- Feature Engineering & Delivery: Design, build, test, and maintain scalable, secure, and resilient fullstack applications using .NET Core and React.
- Security & Best Practices: Actively address security vulnerabilities across both frontend and backend codebases, adhering to modern secure coding standards and OWASP principles.
- Architecture Implementation: Translate architectural guidelines into clean, maintainable, and well-tested code, contributing actionable technical insights to team design discussions.
- Performance Optimization: Continuously monitor, troubleshoot, and optimize application performance, reliability, and backend/frontend interactions.
- AI Tooling & Developer Velocity: Utilize AI tools and agentic workflows (e.g., Claude Code) to accelerate feature delivery, cross-file refactoring, and automated testing.
- Quality & Testing Ownership: Drive test coverage (unit, integration, end-to-end) and enforce robust code quality and CI/CD standards within the development pipeline.
- Team Leadership & Mentorship: Conduct thorough peer code reviews, mentor junior and mid-level developers, and foster a collaborative, continuous-learning culture.

Technical Skills:
- Claude Code Environment Experience: Proficient in using Claude Code via terminal, IDE, and GitHub integrations to accelerate codebase onboarding, cross-file refactoring, and feature delivery.
- Agentic SDLC Experience: Practical experience applying AI agents and AI-driven workflows across the software development life cycle.
- Backend Mastery: Proven experience in backend development with deep expertise in .NET Core (C#) and familiarity with ASP.NET.
- Frontend Engineering: Strong hands-on proficiency in JavaScript, TypeScript, and modern frontend frameworks like React.
- Software Design: Solid understanding of core software development principles (SOLID, DRY) and microservices/monolithic design patterns.
- Data Management: Experience with relational and non-relational databases (e.g., SQL Server, PostgreSQL, MySQL) including query optimization and schema design.
- Cloud & DevOps: Familiarity with cloud computing platforms (especially AWS), containerization, RESTful API design, Git, and automated CI/CD pipelines.

Soft Skills:
Proactive Ownership: Demonstrates initiative by identifying challenges early, proposing pragmatic solutions, and taking end-to-end responsibility with minimal supervision.
- Critical Thinking: Questions underlying assumptions and analyzes problems from foundational concepts up, ensuring deep technical comprehension before taking action.
- Adaptability & Continuous Learning: Eagerness to learn new languages, frameworks, and engineering tools as technical demands evolve.
- Problem Solving: Strong analytical skills with a track record of diagnosing and resolving complex technical issues in production environments.
- Communication & Collaboration: Excellent written and verbal communication skills, with a team-oriented mindset and ability to bridge discussions between product and engineering.
- AI Enthusiasm: A genuine interest in leveraging AI technologies to enhance development efficiency and code quality.

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.