I'm Sieun Kim, a backend developer passionate about building scalable systems and solving real-world problems through clean, reliable code.

My journey began with a curiosity for how things work under the hood—from rooting phones in middle school to exploring network protocols and cloud infrastructure. Now, I’m on a mission to build impactful and accessible services that blend technical depth with thoughtful design.

I enjoy working on projects that matter—like improving access for transportation-vulnerable users, optimizing feed systems under high traffic, and leading green-tech platforms with real-time challenge tracking. Whether it’s collaborating on cloud-native architectures or fine-tuning authentication flows, I love diving deep into problems and finding elegant, efficient solutions.

Let’s build something meaningful together.

• Build with purpose: I strive to create services that are not only functional but also meaningful for users.
• Structure with care: I value readability, maintainability, and thoughtful design in both code and system architecture.
• Lead with empathy: Clear communication and mutual respect are at the core of every successful team.

I thrive in fast-paced environments where learning never stops. As the Backend Lead in multiple projects and a captain of the AWS Cloud Club, I’ve tackled everything from API bottlenecks to multi-AZ deployments. My favorite tools are Spring Boot, Redis, MySQL, and a good debugging session.

I believe growth happens when we share and reflect. That’s why I document my challenges, mentor others, and welcome constructive feedback.

Whether I'm scaling a service for 10,000+ users or guiding teammates through tech decisions, I aim to build robust, user-centered systems that stand the test of time.

• Java 21, Spring Boot 3
• MySQL 8, Redis (with Bloom Filter)
• Spring Security, JWT
• Docker, AWS, GCP, GitHub Actions
• JUnit5, Mockito, JaCoCo, Gradle

• Scaling Leafresh, a real-time eco-challenge platform (Backend Lead)
• Writing API integration and edge-case tests with JUnit + JaCoCo
• Documenting domain tech specs and async architecture (event-driven, SSE)
• Exploring Redis caching strategies (Time Deals, Posts) and SQS-based decoupling
• Managing these tasks in parallel to ensure seamless QA and architectural clarity

• GitHub: @seplease
• Blog: rec-of.tistory.com
• Email: kimsieun.direct@gmail.com