Desenvolvedor .NET Sênior — (C# / SQL Server / AppSec)

This position is listed on behalf of a partner company, which manages all applications and next steps. Our partner is looking for a Desenvolvedor .NET Sênior — (C# / SQL Server / AppSec) based in Brazil.
In this role, you will develop, maintain, and secure enterprise applications, combining advanced .NET engineering with database optimization and application security practices. You will contribute to the evolution of existing systems while ensuring the reliability and integrity of critical business operations. Working across backend development, SQL Server performance, and application security, you will help identify vulnerabilities and implement robust safeguards against potential threats. You will also strengthen secure development practices through code reviews, automated testing, and security checks integrated into CI/CD pipelines. Your work will be particularly important in protecting sensitive data, preserving transactional accuracy, and supporting compliance and audit requirements. This is an opportunity to take technical ownership, solve complex engineering challenges, and make a measurable impact in a quality-focused, security-conscious environment.
Accountabilities
Develop new features, fix bugs, refactor existing code, and improve application performance using C#, .NET Framework, modern .NET, ASP.NET Core, Web API, and MVC.
Maintain and modernize legacy applications while preserving existing business rules, functional behavior, and critical financial processing workflows.
Optimize SQL Server databases by improving T-SQL queries, stored procedures, indexes, transactions, and execution performance.
Identify, assess, and remediate application vulnerabilities, including insecure SQL queries, authentication weaknesses, authorization flaws, and risks involving sensitive data.
Implement secure coding practices to mitigate common vulnerabilities such as SQL Injection, Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF), Server-Side Request Forgery (SSRF), and insecure direct object references (IDOR/BOLA).
Review and strengthen API security through appropriate authentication, authorization, access validation, and secure integration mechanisms.
Conduct code reviews, develop regression tests, and integrate security validation into development and deployment pipelines.
Implement and maintain application security tools and processes, including static application security testing (SAST), dynamic application security testing (DAST), and software composition analysis (SCA).
Ensure transactional integrity, operational traceability, appropriate segregation of duties, and protection of financial positions and transactions.
Apply idempotency controls and maintain technical evidence, logs, and audit trails to support investigations, compliance, and audit requirements.
Collaborate with technical teams to improve software quality, strengthen security controls, and reduce operational and business risks.
Requirements
Strong professional experience in software development using C# and .NET, including .NET Framework, modern .NET, ASP.NET Core, Web API, and MVC.
Advanced knowledge of Microsoft SQL Server, including T-SQL, stored procedures, transactions, indexing, query optimization, and database permissions.
Solid understanding of secure coding principles and the OWASP Top 10, with practical experience identifying and addressing SQL Injection, XSS, CSRF, SSRF, and IDOR/BOLA vulnerabilities.
Experience securing APIs and implementing authentication and authorization mechanisms using OAuth 2.0, OpenID Connect, JWT, and robust access validation.
Practical knowledge of application security (AppSec), including vulnerability assessment, secure code reviews, SAST, DAST, and SCA.
Experience maintaining and supporting legacy applications, including environments involving IIS, Windows Server, integrated authentication, and application integrations.
Understanding of transactional integrity, access segregation, data protection, and secure processing of sensitive business information.
Strong analytical and problem-solving skills, attention to detail, and the ability to assess technical risks without compromising critical business functionality.
Ability to work independently, prioritize technical issues, communicate clearly, and collaborate with development and security stakeholders.
Nice To Have
Knowledge of SOLID principles, Clean Architecture, automated testing, and API design best practices.
Experience with DevSecOps practices, Git, CI/CD pipelines, SonarQube, Snyk, or equivalent tools.
Familiarity with encryption, secrets management, TLS, secure logging, and audit trail implementation.
Experience in financial services, particularly investment funds, portfolios, financial positions, transaction processing, or reconciliation workflows.
Benefits
Remote work: Fully remote working arrangement, offering flexibility and location independence within Brazil.
Contract type: Independent contractor (PJ).
Life insurance: Coverage designed to provide additional financial protection.
iFood Livre: Access to the iFood Livre benefit program.
TotalPass: Access to a fitness and wellness platform supporting physical activity and well-being.
Technical impact: Opportunity to work on application security, backend engineering, database optimization, and the protection of critical business systems.
Professional growth: Exposure to secure software development practices, vulnerability management, and modern DevSecOps approaches.
How Jobgether Works
We use an AI-powered matching process to ensure your application is reviewed quickly, objectively, and fairly against the role's core requirements. Our system identifies the top-fitting candidates, and this shortlist is then shared directly with the hiring company. The final decision and next steps (interviews, assessments) are managed by their internal team.
We appreciate your interest and wish you the best!
Why Apply Through Jobgether?
Data Privacy Notice: By submitting your application, you acknowledge that Jobgether will process your personal data to evaluate your candidacy and share relevant information with the hiring employer. This processing is based on legitimate interest and pre-contractual measures under applicable data protection laws (including GDPR). You may exercise your rights (access, rectification, erasure, objection) at any time.
We may use artificial intelligence (AI) tools to support parts of the hiring process, such as reviewing applications, analyzing resumes, or assessing responses and identifying potential inconsistencies or verification signals in application materials based on available information. These tools assist our recruitment team but do not replace human judgment. Final hiring decisions are ultimately made by humans. If you would like more information about how your data is processed, please contact us.

Work arrangement
Yes