JungJun Sung

@JungJun-Sung

Full-Stack Developer | React, Next.js & Cloud Enthusiast (AWS/Docker)

Ottawa, ON, CanadaJoined January 2026

About

Full-Stack Developer with 3+ years of expertise in the JavaScript ecosystem (React, Next.js, TypeScript, Node.js). Currently operating as an independent developer, architecting and shipping scalable products including a global travel platform. I am passionate about building efficient, type-safe web architectures and actively expanding my expertise into Cloud Engineering with AWS, Docker, and Kubernetes.

Available for

Full-time opportunities in Canada & US. Open to interesting side-projects or technical co-founding roles involving AI/SaaS.

JungJun Sung's blogs

JungJun's Engineering Journaljungjun-sung.hashnode.dev6 posts

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Recently published

JSJungJun Sungjungjun-sung.hashnode.devFeb 15 · 6 min read

MongoDB Schema Design: Lessons from Production

MongoDB schemas are flexible. That’s exactly why designing them is difficult. Here are the schema design patterns I learned while building Roavelo. Embedding vs Reference This is the most important decision in MongoDB schema design. Embedding: Countr...

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JSJungJun Sungjungjun-sung.hashnode.devFeb 9 · 5 min read

React Native Performance Optimization: Patterns I Actually Applied

Performance issues in React Native apps mostly come from list rendering and images. Here are the optimization patterns I applied in Roavelo. FlatList Optimization FlatList is the most commonly used component in React Native, and also the one that nee...

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JSJungJun Sungjungjun-sung.hashnode.devFeb 7 · 7 min read

Payment System with RevenueCat

Following authentication, I decided not to build payments from scratch. The reasoning is similar. Why RevenueCat Building in-app purchases yourself requires: - Apple StoreKit 2 implementation - Google Play Billing Library implementation - Receipt ver...

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JSJungJun Sungjungjun-sung.hashnode.devFeb 6 · 9 min read

How Clerk Saved Me Two Weeks

One of the first decisions I made when starting Roavelo was not to build authentication from scratch. Why Clerk I needed to ship the MVP quickly. Building auth from scratch would take at least 2-3 weeks. - JWT sign/verify logic - Refresh token rotati...

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JSJungJun Sungjungjun-sung.hashnode.devFeb 5 · 13 min read

What I Learned Separating Server State from Client State

Building the Roavelo mobile app, I ended up using TanStack Query and Zustand together for state management. This post covers why I picked that combo, what worked, what didn’t, and some real patterns like Optimistic Updates and payment data validation...

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JungJun Sung

About

Available for

JungJun Sung's blogs

Recently published

MongoDB Schema Design: Lessons from Production

React Native Performance Optimization: Patterns I Actually Applied

Payment System with RevenueCat

How Clerk Saved Me Two Weeks

What I Learned Separating Server State from Client State

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JungJun Sung

About

Available for

JungJun Sung's blogs

Recently published

MongoDB Schema Design: Lessons from Production

React Native Performance Optimization: Patterns I Actually Applied

Payment System with RevenueCat

How Clerk Saved Me Two Weeks

What I Learned Separating Server State from Client State