Despite the pandemic, e-commerce behemoth Amazon (AMZN -2.56%) managed to come out on top in 2020. Fourth-quarter revenue was up 44% year over year, driving a 77% improvement in operating income. The full-year results are just as impressive as consumers flocked to the online shopping platform while locked down at home. Given this backdrop, it's not surprising Amazon shares are up more than 60% in the past year.

The company threw a curveball in conjunction with its fourth-quarter results, however. Amazon's founder and chief of over 27 years, Jeff Bezos, will be stepping down from that role later this year. Thus begins an era when the names "Bezos" and "Amazon" are not nearly as synonymous.

Investors aren't quite sure how to respond. Rather than the fourth quarter's sales and earnings beats catapulting the stock higher (and out of a five-month funk), the stock slipped just a bit on Wednesday. The market is still looking for clues as to how incoming CEO Andy Jassy, who currently serves as the chief of Amazon Web Services (AWS), might change things. After all, the company is so much more than its cloud computing business. Some may even be mulling a more broad-based bet like the SPDR S&P 500 ETF (SPY -0.87%) instead of taking a shot on a proven company close to being helmed by an unknown leader.

And for now, that's probably the best move most investors can make.

Woman's toes on a sidewalk, in front of chalk arrows pointing in different directions.

Image source: Getty Images.

A changing of the guard

It's tough stuff to process. Most companies are bigger than their CEOs. There are some exceptions to this premise, however. Older investors may recall that General Electric was never quite the same after Jack Welch retired. Tesla wouldn't be what it is today had Elon Musk not been so determined to revolutionize automobiles. Bezos seemingly willed his company into becoming the defining name in e-commerce, pushing through the lean early years when it wasn't clear Amazon would ever achieve sustainable viability. He'll soon be gone, so now what?

Giving credit where it's due, Jassy has proven he's got a grip on the business that will keep growing once the COVID-induced online shopping surge cools off. AWS revenue grew 30% last year, leading to a 47% improvement in the operating income it adds to Amazon's bottom line. That growth mirrors the division's expansion since its start in 2006 but now within a cloud computing market that's increasingly competitive as powerhouses like Alphabet and Microsoft keep stepping up their games.

Jassy's more than just a cloud guy, though. While he may have less experience with front-line, generalized online consumerism than his predecessor does, he is showing us an affinity for new growth engines. Case in point: He's a big believer in the potential of video gaming. Amazon is in the business, but it isn't particularly competitive within the space that's soon going to be worth $200 billion per year. This opportunistic interest suggests Jassy's more than a tech-head.

There's something else, however, that should discourage you from stepping into Amazon shares just yet.

One too many unknowns

Bezos's exit couldn't be any more difficultly timed. The company's facing myriad challenges that have been brewing in the background for years but are now being pushed to the forefront in a big way.

Yes, the controversial decision to remove alternative social networking site Parler from Amazon's servers is one of them, although those headlines aren't the hurdle. They're a symptom of a much bigger philosophical issue: How much control should "big tech" have on the operations of the companies it serves? It's a question that's been kicked around at the congressional levels for years and particularly among the Democratic party that's now in power in Washington D.C.

In the same vein, antitrust concerns here and abroad continue to circulate.

None of these challenges are insurmountable. But they're somewhat new for Jassy, even if Bezos is remaining at his side as the company's executive chairman.

Of course, the lack of certainty on the regulatory front only exacerbates what's perhaps the biggest risk in owning Amazon stock at this time -- investors as a group may simply be unwilling to bet on Amazon during this transitional period. Underscoring this uncertainty is whether or not Amazon will be able to sustain its current growth trajectory once the pandemic is abating.

While not devastating, Wednesday's slight pullback in response to the impressive quarter is a subtle indication of these doubts. It could take months for the market to reestablish the sort of confidence it had in Amazon when Bezos was in charge.

Keep it in perspective, but don't ignore the risk

Don't overreact to the warning. Amazon is far from doomed, but there's a lot of change on the horizon. That tends to work against a stock.

The broad market also poses risks of its own right now, to be sure. We don't exactly know how quickly stocks might overcome the effects of COVID-19, for instance. We do know, however, that the fourth quarter's GDP grew on the order of 4%, while Standard & Poor's estimates fourth-quarter earnings for the S&P 500 are going to be around twice the second quarter's coronavirus-crimped levels. On a risk-versus-reward basis, an index-based trade is the smarter option of the two right now. There's a lot to be said for knowing just what you're getting for your money.