Businesses with great growth stories and plenty of runway ahead of them tend to get a lot of attention. A few inevitably tend to slip under the radar, though, especially those that fall under the "mid-cap stock" category -- those that are big enough that there might be some recognition, but not big enough to garner household name status as the world's biggest companies.

These in-the-know operations can still offer up big gains for patient investors, though. Three of them that contributors picked out for your consideration are Arista Networks (NYSE:ANET), Royal Caribbean (NYSE:RCL), and NIO (NYSE:NIO).

Data centers are getting an upgrade

Nicholas Rossolillo (Arista Networks): Perhaps you've never heard of 400G technology, but there's a good chance you will be the beneficiary of its eventual adoption. The "G" in 400G refers to the speed at which a data center can process packets of information, and the latest standard is four times faster than the 100G tech that has been around the last few years. As ultra-high-definition video streaming, video game streaming, artificial intelligence services, and other related computing needs continue to become more significant, data centers are under pressure to take on bigger and more complex tasks.

That's where Arista Networks comes in. The data center hardware and service provider is still small, but it's growing fast. Later this year the company's first 400G platforms will start shipping to customers, adding another possible growth driver to the mix. It could take some time for the new tech to gain traction, but the world's internet traffic is only increasing, providing a strong tailwind for the company in the years ahead.

In the meantime, older data center technology upgrades are still providing plenty of momentum. For full-year 2018, management said to expect a 40% increase in sales over 2017, which should result in an even bigger increase in the bottom line. The stock's 12-month forward price-to-earnings ratio is currently 23.6. Paying for a quarter century's worth of profit may not be palatable to every investor, but that could be a fair price to pay for a company growing as fast as Arista is.

Data centers and the cloud computing services they support are set to continue growing for years, and Arista is at the forefront of the movement. With momentum pushing sales higher and a new upgrade cycle getting ready to launch, now could be a great time to consider a purchase.

Check out the latest Arista earnings call transcript.

A young woman with a thought bubble and bag of money drawn above her head.

Image source: Getty Images.

The bigger the boat, the more fun

Chuck Saletta (Royal Caribbean): When it comes to cruise lines, there are incredible benefits to having big boats. The larger the boat, the more passengers the fixed manufacturing and operating costs can be spread across, and the more amenities the cruise company can offer its passengers. From that perspective, Royal Caribbean is well situated, with the four largest cruise ships out there and 10 of the top 15. 

Perhaps most importantly from a growth perspective, Symphony of the Seas, Royal Caribbean's largest of them all, first set sail with passengers in late March 2018. That means it still has time before it laps its first year in operations, thus magnifying its ability to drive near-term growth. As if that weren't enough, Royal Caribbean is planning to launch an even bigger boat in 2021, creating yet another opportunity for more size-fueled growth.

You may not initially think of a company that was founded in 1968 as a growth business. Still, in-the-know investors recognize that Royal Caribbean is expected to grow its earnings by a respectable 12% annualized over the next five years, driven by its continued expansion. Combine that growth with the fact that it's available at around 10 times its anticipated earnings and you have a business that offers both reasonable growth and a reasonable value.

Of course, in a capital-intensive, economically sensitive business like owning and operating the world's biggest cruise ships, there is a risk that an economic slowdown could cause the company to stumble. But even then Royal Caribbean looks reasonably positioned thanks to a solid balance sheet with a debt-to-equity ratio of around 0.9. Should an economic downturn throw its growth trajectory off track, it may knock the business down, but it likely won't knock it out.

Check out the latest Royal Caribbean earnings call transcript.

A lucrative and electric future

Daniel Miller (NIO Inc.): The world is inherently unpredictable, and that can make thriving businesses outdated in only a few years -- just ask former Blockbuster executives. But in-the-know investors realize China is pushing consumers to electric vehicles, and that won't be changing. That makes NIO, often referred to as China's Tesla, an intriguing growth stock.

Consider that only 50,000 EVs were sold in China as recently as 2014, but the goal is to sell 2 million electric and hybrid vehicles annually in China by 2020, and as many as 7 million by 2025. As China's middle-class blossoms and car ownership becomes more feasible, the government has started cracking down on pollution by emphasizing EVs. In some major cities, it's already nearly impossible -- and very expensive -- to get a license for a traditional combustion vehicle, whereas an EV license is free and available to anyone.

With China's government pushing consumers toward EVs, that makes NIO, China's premium electric vehicle maker, an intriguing growth stock over the next couple of decades. While the company is a new name to many, in-the-know investors realize how powerful its brand already is. Consider that a broadcast of NIO's first-ever "NIO Day," an event to unveil the new ES8 vehicle in December 2017, had over 110 million views. For context, a few months later Super Bowl LII drew 103.4 million TV viewers.

As China's EV market becomes the most desired, and likely the most lucrative, in the decades ahead, NIO is well positioned to thrive if it can continue to build its brand image and high-quality vehicles. Even notorious short-seller Citron Research has put in a good word, and notes the stock has little resistance to its short-term target of $12. NIO isn't a household name yet, but in-the-know investors realize how bright its future is.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.