After an incredible run last year following the initial round of pandemic lockdowns, 2021 has been a reminder that growth stocks don't go up in a straight line. Volatility has struck some top tech names multiple times this year, with everything from a reopening economy (and the return to a little bit of normalcy that has come with it), rising interest rates, and geopolitical concerns weighing on them. 

But investing in growing businesses is a long-term concern, one that pays off handsomely for those who patiently stick with it. Three contributors shared three growth stocks that they're buying right now: Twilio (TWLO 0.88%), MongoDB (MDB 0.24%), and Micron Technology (MU -2.03%).

A top cloud name you'll never see on a consumer product

Nicholas Rossolillo (Twilio): Everyone has now at the very least heard of Zoom Video Communications, with many people making regular use of the cloud-based video conferencing tool. How about Twilio? That's not exactly a household name. Yet Twilio is another giant in cloud communications, albeit one working quietly behind the scenes powering all sorts of modern business communications. 

Twilio runs a library of APIs (basically, software code that embeds a capability in an app or website) that enable chat, text messaging, voice, video, email, and analytics. Its flagship service Flex is a top solution for the modern contact center, helping organizations do just what the name implies: flexibly stay in touch with customers no matter which method of contact they prefer. 

Did I mention this is a big business? Revenue in Q2 2021 was $669 million, derived from more than 240,000 customers. That represented a 67% increase from the same period last year, and management expects sales will grow at least another 50% year over year in Q3. In spite of this incredible growth, Twilio stock is flat 2021 to-date as it digests a 244% run in 2020. But as revenue has steadily increased at a rapid pace and proven this is more than just a one-off pandemic winner, Twilio shares have gotten cheaper. Shares trade for just shy of 25 times trailing-12-month sales as of this writing.

It's still a premium price tag to be sure, one that implies Twilio will continue to grow at a double-digit percentage clip for at least a couple more years. But given the rapid migration to cloud-based services and Twilio's winning template for business communication success, the company is in good shape to deliver such growth for a long time. Plus, Twilio plows all of its excess cash into development of new products and marketing to sustain its momentum, something it can handily afford to do with its stellar balance sheet featuring over $5.9 billion in cash and equivalents offset by debt of only $985 million. I'm a buyer right now.

Someone in an office working on a smartphone and laptop.

Image source: Getty Images.

This database stock will be humongous

Anders Bylund (MongoDB): A week ago, I said I would buy some more MongoDB shares while the database disruptor's stock was trading at a discount. I followed through on that promise a few days ago. As luck would have it, you can still follow my lead and build your own MongoDB position -- from scratch or on top of an existing investment -- at a similarly attractive price point.

MongoDB isn't the only next-generation database software specialist, but it is an established leader in that explosive field. The company's eponymous flagship product and the cloud-based version sold under the Atlas brand offer simple database creation and management for very large collections of chaotic data sources. The time-honored relational database giants struggle to match MongoDB's suitability for modern software designs, where data comes from messy real-world sensors and direct input from end-users.

So MongoDB holds the reins to the data collection, organization, and analysis needs of the present and of the future. That's a business I want to invest in, especially when share prices are pulling back from their relatively constant skyrocketing trajectory.

And that's what MongoDB offers right now. The stock has restarted its long-term climb from the recent lows of early May, but MongoDB shares are still trading 15% below February's all-time highs. I took action on this opportunity a few days ago. You can do the same right now if you're interested in a fantastic growth stock with a moat made of innovative software solutions.

The cheapest stock in the tech sector

Billy Duberstein (Micron Technology): Shares of Micron have sold off hard recently, but is it really justified? I think not, which is why I recently added to my stake.

The reasons for the sell-off are related both to the macroeconomic picture, as well as specific fears related to the memory industry, where Micron is one of just a few main players. On the macroeconomic front, rising delta variant COVID-19 cases have prompted fears of a cyclical slowdown in economic growth. Micron has traditionally been a highly cyclical stock, and tends to trade lower when fears of an economic slowdown come to the surface.

But if you think about it, Micron actually did quite well in the unique COVID-19 slowdown of 2020, because its memory chips are the horsepower that powers the digital economy. So when demand increased for phones, PCs, and cloud computing data center servers, demand actually remained very strong for many of Micron's segments. So if we revert to a more stay-at-home economy, it may not be such a bad thing for Micron.

For Micron specifically, the stock took a precipitous hit when Morgan Stanley recently downgraded Micron from overweight to equal weight. Morgan Stanley analysts are worried that the DRAM pricing is peaking. In the past, oversupply has led to precipitous declines in DRAM pricing, and therefore Micron's revenue and earnings. Micron's stock tends to move with DRAM pricing, as DRAM memory accounts for more than two thirds of Micron's revenue.

And yet, again, these fears may be overblown. For one, Morgan Stanley lowered its price target from $105 to $75, still about $5 more than the $70 at which Micron trades today. That's already down some 27% from all-time highs back in the spring, and probably pricing in some declines already.

Second, there is no guarantee that Morgan Stanley is correct about an upcoming DRAM price crash. DRAM prices have been skyrocketing higher in the first half of 2020, and are now slowing -- but that doesn't necessarily mean a big crash. In fact, Morgan Stanley's call is not the current consensus on Wall street. Rosenblatt Securities analyst Hans Mosesmann still thinks the current DRAM cycle will be "extended and large." Meanwhile, MKM Partners' Dan Foreman commented on the Morgan Stanley downgrade as likely marking a near-term bottom for the stock. The average analyst price target is still $115, about 65% higher than today's price.

Meanwhile, Micron's recent earnings and outlook have been incredibly strong -- strong enough to the point where management felt comfortable enough to initiate a dividend. That decision likely wasn't made lightly, showing confidence that the cycles of the past may be less severe going forward.

The last memory price crash came after a huge run-up in supplier capital expenditures, which ran right into the U.S.-China trade war. The trade war caused a demand shock that sparked a memory recession. But today, supplier capex has been disciplined, and although growth may slow due to the delta variant, I don't think it will approach the shock of the onset of the trade war.

Trading at just 6.5 times next year's earnings estimates, one would be hard-pressed to find a cheaper stock in the technology sector.