Big returns on the market can sometimes come unexpectedly. Putting money into growth stocks with a lot of potential upside can deliver life-changing returns. Typically, however, that happens over years, maybe even decades. But given just how hot the S&P 500 has been, it may not be all that surprising that many investors could have gotten incredibly rich by just investing at the start of 2023.

Three stocks that have posted monstrous returns for investors over the past two years are AppLovin (APP 0.16%), MicroStrategy (MSTR -5.21%), and Carvana (CVNA -1.09%). Investing $11,000 into each of these stocks at the start of 2023 would have generated more than a $1 million profit for you as of the end of last year. Here's a look at why these stocks have done so well, and whether they are still good investments today.

AppLovin

AppLovin helps businesses monetize mobile games. It has recently expanded into a new vertical in e-commerce, which has investors excited about how much more growth may be on the horizon. The tech company has been a growth machine, with its sales totaling $3.3 billion through the first nine months of 2024, rising 43% on a year-on year-basis. During that time, its bottom line jumped by more than 430% to $980.6 million.

AppLovin wasn't always this great a growth stock. It was unprofitable in 2022, with just minimal top-line growth. But with the company posting impressive results in recent quarters and now being part of the Nasdaq-100 index, the momentum has been carrying the stock higher in recent months. An $11,000 investment in the tech stock at the start of 2023 would have grown to a value of around $339,000 as of the end of last year.

Despite its impressive gains, however, I'd hold off on buying shares of AppLovin, as its valuation is incredibly high. Currently, the stock trades at a whopping 100 times its trailing earnings and nearly 28 times revenue. While investors are optimistic about its future growth opportunities, my concern is that a lot of that growth is already priced into the stock's valuation.

MicroStrategy

Another incredibly hot stock over the past couple of years has been MicroStrategy. An $11,000 investment at the start of 2023 would have ballooned to a massive $225,000 two years later. While the company is involved in offering business intelligence solutions, its bullish strategy on Bitcoin is what has propelled its valuation so high.

MicroStrategy has been loading up on bitcoins and is easily the largest corporate holder of them, with 450,000 as of Jan. 20. The company is still planning to add more, which means that as the price of Bitcoin goes, its shares are likely to follow in the same direction. Like AppLovin, MicroStrategy was also recently added to the Nasdaq-100, meaning more investors will have exposure to it.

This isn't a stock I'd invest in today, however, as there can and will be significant fluctuations in crypto. MicroStrategy has also incurred a loss in three straight quarters. This isn't going to be a suitable stock for most investors, given the high risk that it carries.

Carvana

The biggest gains on this list belong to investors who took a chance on Carvana a couple of years ago. Since it was facing the threat of potential bankruptcy, investing in the stock would have involved taking on substantial risk.

But those investors who went ahead taking that risk would have been rewarded handsomely. An $11,000 investment in the business at the start of 2023 would have grown to a massive $472,000 as of the end of 2024. Combined with the other risky investments listed here, the value of all these holdings (assuming an $11,000 investment in each stock) would have been worth more than $1 million as of the start of this year.

Carvana is an online used-car retailer which has struggled with profitability in the past. An increase in interest rates made financing more difficult for customers a few years ago, which weighed on its financials. But with economic conditions improving and multiple interest rate cuts, the future has begun to look more promising for Carvana, and the company has now posted a modest profit in each of its past three quarters.

However, profit margins remain tight and the economy's still not in great shape. That's why I'd still steer clear of this stock, despite its impressive recovery over the past few years.