There's no denying it: Amazon (AMZN -0.72%) has been one of the market's most rewarding stocks of the modern era, gaining more than 270,000% since its initial public offering in 1997.

It's still going pretty strong, too, leveraging not just its dominance of an ever-growing e-commerce market but also its lead in a burgeoning cloud computing industry. This year's and next year's top lines are both expected to grow by about 10%, with earnings predicted to improve even faster.

As veteran investors can attest, however, nothing lasts forever. Yesterday's darlings can turn into tomorrow's disappointments, often weighed down by their sheer size resulting from years of unfettered growth. That certainly seems like a possibility in Amazon's case.

To this end, investors on the hunt for the proverbial "next big thing" may want to consider stepping into two other unstoppable growth stocks rather than Amazon.

Here's a closer look at each one.

1. Uber Technologies

Anyone keeping tabs on Uber Technologies (UBER 1.75%) likely knows the ride-hailing giant's fourth-quarter numbers were a disappointment. Despite topping revenue estimates, operating income fell short of expectations.

Guidance for the quarter now underway was also lackluster at a time when investors are increasingly concerned about the impact that robotaxis could soon have on its business. All told, Uber stock tumbled following the early February release of those numbers.

But there's a reason that the pullback quickly turned around to carry shares to highs above its pre-report price. This company is plugged into a movement that's much bigger than just one single quarter.

In short, automobile ownership (and even attaining a driver's license) is falling out of favor. Although a large number of people living where Uber does business will always want their own vehicle and need a driver's license to use it, both numbers are shrinking -- and are likely to continue declining.

Car-sharing company Zipcar says roughly one-third of car-owning adults currently living in the United States are likely to no longer own one by 2030. Blame cost and inconvenience, mostly. It's now often cheaper and easier to just pay for a ride.

And the Federal Highway Administration reports that less than 40% of U.S. teenagers now have a license, versus two-thirds of teens 30 years ago. For the same reason, too: It's now cheaper and easier to outsource mobility.

As this cohort of the population ages and has their own children, they're likely to pass along and even encourage continued growth of car-lessness and the continued demand for ride-hailing.

That's what Straits Research suggests with its industry outlook. It's predicting the ride-hailing market is set to grow at an annualized pace of more than 11% through 2032. Analysts expect Uber Technologies sales growth to outpace this number at least through 2027, underscoring its dominance of the U.S. sliver of the global ride-hailing business.

Data source: StockAnalysis.com. Chart by author.

But what about the rise of robotaxis? It's something to watch to be sure.

However, the technology for autonomous vehicles is still in its infancy. It could be years before it's a threat to Uber's business, and that assumes the company itself won't embrace the idea -- which it appears to be doing. Just this week, it announced that anyone hailing a ride in the Austin, Texas, area might be offered one using Alphabet's Waymo self-driving tech.

If autonomous driving is the future, Uber Technologies seems to be getting ready for it.

2. SoFi Technologies

The other unstoppable stock to buy instead of Amazon is another consumer-facing name whose technology makes life easier. That's SoFi Technologies (SOFI 1.12%). It's an online bank, although that description doesn't do it justice; most major banks now offer at least some degree of online service.

SoFi is different in that it was built from the ground up to be nothing but an online bank, yet it still offers all the services you would expect from a conventional brick-and-mortar bank, including checking accounts, investing services, loans, insurance, and credit cards.

It seems like a big leap for a business that for centuries has operated on an in-person basis. It's not quite as much of a leap as you might imagine, though.

A survey performed last year by the American Bankers Association indicates that 55% of the nation's bank customers cited a mobile app as their first option for handling banking business. The next-nearest choice was an online interface (using a conventional computer's web browser), with 22% of respondents saying that was their go-to choice. In-branch visits and telephone calls, conversely, were preferred by only 8% and 4%, respectively, in the survey.

SoFi Technologies is simply doing business where people are increasingly going. And it has the growth in customer head count to prove it.

Data source: SoFi Technologies Q4-2024 earnings call deck.

The industry is almost certainly going to continue moving in this direction, if the age breakdown of the survey's respondents is any indication. Digitally native Gen Zers and millennials are more likely than average to use a mobile banking app, with 64% and 68% (respectively) of these two groups naming it as their first choice for banking.

As with car ownership and drivers' licenses, too, these cohorts are not only likely to pass along these new banking norms to younger generations, but also accelerate the shift away from brick-and-mortar banking.

Perhaps the crux of the bullish argument here, however, is just how small SoFi Technologies is compared to the growth opportunity at hand.

With just about 10.1 million customers using a little less than 14.8 million of SoFi's products or services in total, the online bank has only scratched the surface of what it could become. For perspective, the United States is home to 340 million people, living in more than 127 million households. Even then, however, SoFi could continue to grow simply by selling its existing members more products and services than they currently use.

And Straits Research expects the global online banking business to grow at an average pace of nearly 14% through 2030. The North American market where SoFi operates should remain its biggest region for this time frame.