The technology sector experienced fast-paced growth in 2020 as investors looked to tech companies as a safe place to grow their investments during the pandemic. 

The U.S. hasn't put the coronavirus crisis fully behind it yet, but some investors are already looking beyond the tech sector for new areas of promise as the economy opens back up. This has caused the share prices of some tech stocks to fall from their recent highs, creating good buying opportunities for investors interested in Roku (NASDAQ:ROKU), Okta (NASDAQ:OKTA), and The Trade Desk (NASDAQ:TTD). Here's why.

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Roku's video-streaming platform is firing on all cylinders

Roku's share price is down about 10% over the past three months, and while it may not be cheap in the traditional sense of stock valuations, this dip has created an opportunity for investors to buy the video-streaming specialist's shares at a slight discount. 

The company is coming off of a phenomenal year of growth, ending its fourth quarter with 51 million active accounts (up 39% year over year) and revenue growth of 58%.

The company has benefited from an influx of video-streaming services (think Netflix, Hulu, Disney+, Amazon Prime, HBO Max, etc.) that all use Roku's platform to deliver their content to users. Roku makes money when users sign up for a streaming service through its platform, so the more video-streaming subscriptions available, the better. 

Roku's average revenue per user increased 24% in 2020, indicating that users are signing up for more services than ever before. But even if that trend slows down (you can only sign up for so many services, after all), the company still has other growth opportunities, including advertising.

Monetized video ad impressions more than doubled in the fourth quarter of 2020, and Roku just announced last month that it's buying Nielsen's advertising platform. This should boost the company's ability to sell ads and help it tap into the connected-TV ad market, which eMarketer projects will be worth $18.3 billion by 2024 (up from $11.4 billion this year).  

Roku's video-streaming platform has more users than ever before, it's earning more money from those users, and the company is tapping further into the growing connected-TV ad market. Add to all of that the fact Roku's shares are down over the past three months, and the stock looks like a good buy right now. 

The internet needs more safety, and Okta is helping

Companies are desperately trying to find new ways to manage their websites and data so their users and employees only have access to the information they're supposed to have access to. This online gatekeeping has become even more important after many people started working from home last year. 

That's why Okta's identity and access management (IAM) services are a no-brainer for many businesses. Its platform allows users to log into their accounts safely and helps them retrieve access when they've been locked out, making online account management much easier for IT teams. 

For Okta, the opportunity is huge. The company says its total addressable market in IAM is currently $55 billion and will soon reach $80 billion. Okta is successfully tapping into this space, with fiscal 2021 (which ended on Jan. 31) sales increasing 43%, subscription revenue jumping 44%, and the number of customers with annual contracts worth $100,000 or more up 33% over the prior year. 

Investors have an opportunity to tap into Okta's recent growth right now as its share price has just barely recovered from the recent decline. But don't expect the company's stock to stay stagnant for long. Okta's management estimates revenue will increase 30% in fiscal 2022, and as the company continues to grow, I suspect investors will flock back to this stock.

The Trade Desk taps into the massive advertising market

If you're unfamiliar with The Trade Desk, the company has a robust advertising platform that businesses use to put their targeted ads all across the internet and on connected TVs. 

The Trade Desk makes money by taking a cut of the advertising dollars its users spend on its platform. And with the global digital advertising market estimated to be worth $526 billion in 2023, those small slices of ad spending add up fast. 

The Trade Desk's revenue spiked 48% in the most recent quarter, and the company's adjusted EBITDA margin expanded to 48%, up from 39% in the year-ago period. Not only are its sales and margins moving in the right direction, but The Trade Desk has reported a high retention rate for its customers -- over 95% -- each quarter for six consecutive years.  

Some may be wondering what will happen with the company as Apple and Alphabet's Google begin to move away from online cookies, which track users and are used for targeted ads. But investors' fears may be overblown as the Trade Desk is working with Google and others on an alternative to cookies, which will allow for both targeted ads and increased online privacy for users.

Even with some near-term headwinds from the shift away from cookies, The Trade Desk's management still estimates that sales will grow 34% at the midpoint of guidance in the first quarter of this year. 

The Trade Desk is one the top independent ad-buying platforms, and with its stock currently down about 5% over the past three months, now looks like a good time to snatch up some shares of the company.

Don't forget this last step

If you buy shares of any of the companies above, remember this one last investing step: Hold the stock for years. Tech stocks, in particular, have a habit of riding the market's waves and can tempt even the most steadfast of investors to reach for the sell button. But these stocks should be able to outpace the broad market's returns long term if you can remain patient.

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.