Júlio César Siqueira

I am a Senior Software Engineer with 9+ years of experience specializing in the Kotlin and Java ecosystems. My expertise lies in building high-scale, mission-critical applications that serve millions of daily users, specifically within the Fintech, Retail, and Real Estate sectors.

I define myself as a "Product Engineer"— I bridge the gap between high-performance Android interfaces and scalable Spring Boot backends. I don't just build features; I design entire systems where APIs and UIs work in harmony to handle high concurrency and complex business logic.

I am a strong communicator, comfortable working in English-speaking environments, and experienced in collaborating with distributed global teams.

Technical Expertise

• Mobile: Android (Jetpack Compose, Coroutines, Flow), Kotlin Multiplatform (KMP)
• Backend & Systems: Kotlin/Java, Spring Boot (Security, MVC, Data), RESTful API Design, Microservices, SQL, JPA, Flyway, CI/CD (GitHub Actions), Swagger, Docker, AWS
• Frontend: HTML, CSS, Tailwind, React.js, Typescript
• Architecture & Quality: Clean Architecture, SOLID, DDD, MVVM/MVP/MVC, Unit Testing (JUnit, Mockk, Mockito)
• AI Tools: Copilot, Cursor, Prompt Engineering, Claude Code

Key Impact & Achievements

• High-Scale Retail: Engineered features for a major retail platform with 5M+ downloads, optimizing data synchronization and app performance for peak traffic events.
• Fintech & Payments: Led the development of credit card management systems and implemented low-level EMV/Magnetic stripe logic for SmartPOS terminals.
• Real Estate Platforms: Developed high-availability features for platforms with 300k+ daily active users, focusing on low-latency data fetching and AI-powered search.
• Technical Leadership: Mentored cross-functional teams, fostering a culture of high code quality, automated testing, and agile efficiency.

Featured Architecture & Projects

Mobile Projects