Founded an software development agency while studying at École 42 — closed a $37K contract right after launch and delivered it end-to-end.

Joined early-stage startup Stave as the frontend lead and Built Handybus from 0 to 1 — grew it to 60K registered users and 100K MAU, generating $500K in revenue, including $200K in a single month.

Founded an alumni conference for the global École 42 community from scratch, hosted in Seoul — personally recruited every speaker, sponsor, and the venue, securing sponsorships from 10 companies and selling 300 paid tickets, while leading a 20-person staff across four teams.

• When a Startup Should Pay Down Its Tech Debt: Building HandyParty's Automated Dispatch System (Post url)

• Resolving the Race Condition Between WebView Navigation and the Page Lifecycle (Post url)

Junseong is a thoughtful engineer who always looks for better ways to improve our product. When working with designers, he understands their vision and shares his technical expertise to solve problems together. He plays a key role as a bridge between Backend, Frontend, and Design, making our collaboration much more efficient. Also, he enjoys sharing new knowledge and helps the entire team grow together. Having Junseong on our team is a great strength, and I truly enjoy working with him.

He is the kind of colleague who consistently inspires those around him to explore new ideas and take on exciting challenges together. He brings forward emerging technologies with genuine enthusiasm and a proactive mindset, always eager to experiment and turn ideas into practical outcomes. Beyond his technical capabilities, he also demonstrates a strong understanding of business strategy and contributes meaningfully to the company’s growth and direction. I am continually impressed by his versatility, initiative, and well-rounded perspective as a professional.

He's great at turning ideas into reality. He has a strong sense of what it takes to build an idea all the way into a real service - assembling the right team, shaping the product's direction, and prioritizing the core features. Even the wildest, most far-fetched idea could become real with a teammate like him!

I felt that he has outstanding planning, execution, and communication skills. I was especially inspired by the way he persuades and leads the team.