Chinese startup DeepSeek was Monday hit by outages on its website after its AI assistant became the top-rated free application available on Apple's App Store in the United States.

The company resolved issues relating to its application programming interface and users' inability to log in to the website, according to its status page. The outages on Monday were the company's longest in around 90 days and coincides with its sky-rocketing popularity.

Powered by the DeepSeek-V3 model, which its creators say "tops the leaderboard among open-source models and rivals the most advanced closed-source models globally," the artificial intelligence application has surged in popularity among U.S. users since it was released on Jan. 10, according to app data research firm Sensor Tower.

The milestone highlights how DeepSeek has left a deep impression on Silicon Valley, upending widely held views about U.S. primacy in AI and the effectiveness of Washington's export controls targeting China's advanced chip and AI capabilities.

AI models from ChatGPT to DeepSeek require advanced chips to power their training. The Biden administration has since 2021 widened the scope of bans designed to stop these chips from being exported to China and used to train Chinese firms' AI models.

However, DeepSeek researchers wrote in a paper last month that the DeepSeek-V3 used Nvidia's H800 chips for training, spending less than $6 million.

Although this detail has since been disputed, the claim that the chips used were less powerful than the most advanced Nvidia products Washington has sought to keep out of China, as well as the relatively cheap training costs, has prompted U.S. tech executives to question the effectiveness of tech export controls.

Little is known about the company behind DeepSeek, a small Hangzhou-based startup founded in 2023, when search engine giant Baidu released the first Chinese AI large-language model.

Since then, dozens of Chinese tech companies large and small have released their own AI models, but DeepSeek is the first to be praised by the U.S. tech industry as matching or even surpassing the performance of cutting-edge U.S. models.