Lots of growth stocks have seen some extraordinary growth recently. Netflix, Shopify, and PayPal, for instance, have seen their stocks soar 166%, 97%, and 63%, respectively, over the past 12 months. Growth like this has left many excellent companies trading at questionable valuations. Investors looking to buy fast-growing companies at reasonable prices, therefore, may feel like there aren't any choices left.

But two hot growth still look attractive -- even after recent big run-ups. These stocks are customer relationship management platform salesforce.com (NYSE:CRM) and e-commerce and cloud computing company Amazon.com (NASDAQ:AMZN). Despite rising an impressive 62% and 76% year over year over the last 12 months, these two stocks' underlying businesses still appear to justify their elevated valuations.

Here's a look at why both of these growth stocks remain attractive.

A sketch of a bar chart indicating growth

Image source: Getty Images.

Salesforce

It would be difficult -- if not impossible -- to overlook Salesforce's strong momentum when examining the company's recent quarterly reports.

First and foremost, Salesforce's top and bottom lines are growing very rapidly. First-quarter revenue and operating cash flow, for instance, were up 25% and 19%, respectively year over year. In addition, Salesforce's subscription and support revenue, which accounts for the bulk of the software-as-a-service company's total revenue, was up 27% year over year.

Just as notable is Salesforce management's recent move to hike its revenue guidance for the full year. Salesforce increased its guidance for fiscal 2019 revenue in its last two quarterly earnings releases. Management now expects fiscal 2019 revenue to be between $13.075 billion and $13.125 billion, up from an initial forecast for $12.45 billion to $12.5 billion. 

Of course, this kind of growth doesn't come cheap. Salesforce's trades at about 60 times next year's consensus analyst estimate for earnings per share. But this valuation is better than it looks, as analysts expect Salesforce's earnings per share to rise 27% annually over the next five years. 

Amazon.com

Despite its much larger market capitalization -- $842 billion compared to Salesforce's $104 billion -- Amazon is growing even faster than Salesforce. In Amazon's first quarter of 2018, revenue jumped 43% year over year -- an acceleration from 38% and 34% revenue growth in Amazon's fourth and third quarters of 2017, respectively. 

In addition, Amazon is seeing extraordinary growth in several important segments of its business.

Amazon Web Services (AWS) -- Amazon's most lucrative business segment of all -- is surging. The cloud-computing segment's revenue was up 49% year over year in Amazon's first quarter of 2018 -- and this was on top of 43% year-over-year growth in the year-ago quarter. Over the same timeframe, AWS's operating income jumped from $890 million in the year-ago quarter to $1.4 billion.

Another hot area of Amazon's business is its subscription services, where Amazon recorded 60% year-over-year revenue growth.

Similar to Salesforce, Amazon stock looks pricey on the surface, trading at about 138 times consensus earnings estimates for next year. But as Amazon continues to scale its business, earnings per share could jump sharply. Consider Amazon's 120% year-over-year increase in earnings per share in the company's most recent quarter.

While investors shouldn't expect Amazon's earnings per share to always rise this rapidly, the company's significant lead over its competition gives it unprecedented economies of scale in e-commerce. Once Amazon's biggest growth years are behind it, the company could moderate its reinvestment and benefit from higher profit margins.

Of course, investors are in no rush for Amazon to slow down its big spending. In light of its track record at expanding its business in both existing and new segments, the company essentially has a pass to keep prioritizing growth for years to come.

Despite Salesforce and Amazon stocks' huge increases recently, both stocks still look attractive for investors willing to hold for the long haul.

John Mackey, CEO of Whole Foods Market, an Amazon subsidiary, is a member of The Motley Fool's board of directors. Daniel Sparks has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Amazon, Netflix, PayPal Holdings, Salesforce.com, and Shopify. The Motley Fool has a disclosure policy.