While technology-based startups(TBSs) have been garnering academical and practical attention due to their positive impact on economic growth and job creation, their survival rate remains low. Consequently, numerous scholars have actively explored the factors influencing the performance and survival of the startups. Within this stream of research, this study focuses on the case of Lunit, a successful medical artificial intelligence (AI) startup in South Korea, to examine the key success factors of technology-based startups. This study identifies six key success factors contributing to Lunit's achievements. First, It was founded by a group of individuals with superior expertise and unwavering commitment. Second, It maintained a strong focus on its core business, underpinned by a clearly shared vision. Third, it verifies its technical excellence through notable achievements such as awards, research, papers, and patents. Fourth, it attracted investments from foreign institutional investors. Fifth, it pursued aggressive expansion into foreign markets, surmounting domestic limitations and capitalizing on international opportunities. Last, it harnessed global partnerships to expedite its entry into diverse medical markets across different countries. This study has theoretical implications in that it suggests critical success factors for startups, consistent with prior relevant studies. It also has practical implications by offering insights valuable to policymakers fostering startups and entrepreneurs managing startups.