Last week proved to be a difficult one for growth stocks. Many of the market's fastest-growing technology darlings were slammed, particularly during the second half of the week. The pullback was likely primarily a function of some profit-taking after many of these stocks soared since the bottom of the coronavirus market crash in March.

Sure, many of these stocks were due for a correction. After all, stocks can't trend sharply upward forever. Eventually, they become overvalued. A pullback in these stocks, therefore, was largely merited. But the decline may have also led to some stocks getting oversold.

Three great growth stocks that look like good buying opportunities after last week's sell-off are cloud database company MongoDB (MDB 2.89%), monitoring and analytics platform provider Datadog (DDOG 1.40%), and telehealth and virtual care companies Teladoc Health (TDOC 7.05%) and Livongo Health (LVGO).

A chalkboard sketch of bar charts and a trend line highlighting an upward trend

Image source: Getty Images.

MongoDB: Down 18%

After this week's sell-off, shares of MongoDB are now down 18% from an all-time high, giving today's investors a much better entry point than many other investors have been paying for the stock this summer.

MongoDB has been able to continue growing its business rapidly -- even through the pandemic. The company's revenue for the quarter ending on April 30, 2020 (MongoDB's first quarter of fiscal 2021), rose 46% year over year. This was notably an acceleration from 44% growth in the prior quarter. The company even lifted the low end of its full-year fiscal 2021 revenue outlook by $10 million, guiding for fiscal 2021 revenue to be between $520 million and $530 million.

"While the impact from COVID-19 will be longer than we originally expected at the beginning of this fiscal year, we are seeing clear signs that the current environment is reinforcing the long-term trends toward digital transformation and cloud migration," said MongoDB CEO Dev Ittycheria in the company's fiscal first-quarter earnings release. "MongoDB is a clear beneficiary of these trends and we will continue making investments to fully capitalize on this market opportunity."

Datadog: Down 23%

Shares of Datadog are down 23% since touching a high of $98.99 earlier this month. Yet Datadog's underlying business is booming. While second-quarter revenue growth decelerated from a growth rate of 87% in Q1, it was still up a strong 68% year over year.

The company's customers with contracts boasting annual recurring revenue of $100,000 or more as of the end of Datadog's second quarter were notably up 71% year over year, at 1,015.

Looking ahead, the company provided a full-year outlook for $566 million to $572 million in revenue. Analysts were expecting 2020 revenue of $564 million.

Livongo Health and Teladoc: Down 19% and 23%, respectively

Finally, there's Livongo Health and Teladoc -- two companies whose stocks fell sharply last week after they announced that they planned to cozy up and merge their businesses -- a move that would make them the unquestionable leader in telehealth and virtual care.

The two companies estimate the combination will drive $100 million in revenue synergies by the end of the second year following the close of the merger. In addition, they forecast $500 million of revenue synergies on a run-rate basis by 2025. Considering the two companies generate just $923 million in annual revenue together today, this is quite a projection.

Investors who buy into these telehealth tech companies are taking a stake in an incredible growth story. Livongo Health, a company specializing in virtual care solutions for people with chronic conditions, saw second-quarter revenue surge 125% year over year to $91.9 million. Telehealth platform provider Teladoc saw its second-quarter revenue soar 85% year over year.

Of course, there's always a risk that the merger doesn't close. But even as individual entities, both Livongo Health and Teladoc Health have excellent competitive positioning -- and their shares are down 19% and 23%, respectively, from all-time highs.

Expect more volatility ahead

While these stocks look attractive today, that doesn't mean the prices they saw on Friday will be the lowest they trade from now on. Growth stocks can be very volatile as investors constantly try to reevaluate the present value of share today based on wild forecasts for future growth. Small changes in the sentiment for these companies' growth trajectories can trigger significant swings in their prices.

Looking out five years and beyond, however, these fast-growing tech companies will likely continue winning market share and enhancing their offering for their customers, making them critical technologies of the future and ultimately rewarding investors. More importantly, their scalable business models will likely generate substantial profits over the long haul. But investors will need to exercise patience because these companies are still investing heavily in the big growth opportunities in front of them.