OpenAI will pause accepting new users for its paid ChatGPT Plus service due to overwhelming demand, Chief Executive Officer Sam Altman said in a post on Tuesday.

Altman’s company introduced new features and upgrades at its first-ever developer conference last week, allowing users to build custom versions of ChatGPT to accomplish specific tasks. The announcements triggered a rise in demand for OpenAI’s artificial intelligence tools and services.

“The surge in usage post devday has exceeded our capacity and we want to make sure everyone has a great experience,” Altman wrote on X, the platform formerly known as Twitter.

The AI startup said at its conference that roughly 100 million people use its services every week and more than 90% of Fortune 500 businesses are building tools on OpenAI’s platform.

With the new option, users will be able to create their own specialized versions of ChatGPT — simply called GPTs — that can help teach math to a child or explain the rules of a board game. No coding is required, the company said.

OpenAI also plans to introduce a store later this month where users can find tailored GPTs from other users — and make money from their own — much as they might with apps in Apple Inc.’s App Store.