Amazon (AMZN -0.10%) has been one of the best investments money can buy over its nearly three decades on the stock market. It's up more than 233,000% since its first-day closing price, and if you'd invested $1,000 then, you'd have more than $2.33 million today.

But the growth story isn't finished. There are many reasons to believe Amazon stock can soar some more. Here's the biggest reason why.

An Amazon worker in a mini truck.

Image source: Amazon.

There is a shift to the cloud

One theme CEO Andy Jassy mentions at almost every opportunity is the shift to the cloud. Amazon Web Services (AWS) is Amazon's cloud solutions business, and it's the largest in the world, with 30% of the market, according to Statista. It's one of the company's fastest-growing segments, up 17% in the 2025 first quarter, and it's responsible for most of Amazon's operating income -- 63% in the quarter.

However, according to Jassy, cloud services are still a small percentage of the company's information technology (IT) spend. Jassy says that 85% to 90% of IT spend is still on the premises, but over the next 10 to 20 years, that's going to switch.

If clients were already starting to make the switch before the advent of generative artificial intelligence (AI), they're even more interested now, because the cloud is where there are the greatest opportunities to engage with and benefit from AI. That's a natural growth driver for Amazon, and even more important for the bottom line.

Amazon is investing more than $100 billion in developing its AI business in 2025 alone to offer the most competitive platform and maintain its lead, and it's well-positioned to benefit from the shift to the cloud over the next decade or two. That makes its stock a buy.