It's much better to be a millionaire retiree than a thousandaire one. You're probably not going to become one, though, unless you take some steps toward it. One good way is to regularly invest meaningful sums in the stock market, over a long period of time -- such as via a low-cost broad-market index fund.

If you want to try to get to millionairehood sooner, you might try investing in some carefully chosen individual stocks -- perhaps in addition to investing in index funds. Here are three growth stocks that have a lot of potential.

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1. Zscaler

Zscaler (ZS 0.54%) offers security technology for companies using various cloud services, and has been named the leader in secure web gateways by research firm Gartner. It has been growing briskly, with its stock increasing in value by more than sixfold over only about three years, since the company debuted on the public market. In its most recent quarter, revenue grew by 55% year over year, while billings jumped 71%. The company, recently sporting a market value near $26 billion, "reached a new milestone by surpassing 5,000 customers during the quarter, including 500 of the Global 2000." Between fiscal 2016 and 2020, revenue grew more than fivefold.

Zscaler has a "big, audacious goal" of reaching 200 million users and 100 million workloads, and in a presentation for investors, outlined a handful of growth drivers, such as upselling to existing customers, an increased presence in Japan and Latin America, and continuing technological innovations. The company has excelled at retaining customers and, indeed, at increasing the average amount they spend.

One concern about Zscaler for investors may be that it has been posting net losses, not net income, in recent years. But that's not unusual for younger, smaller companies. They tend to plow as many dollars as possible into furthering their growth.

2. Datadog

Software-as-a-service (SaaS) company Datadog (DDOG 1.28%) has been public for a shorter period than Zscaler. It debuted on the markets in September of 2019, closing at $37.55 per share on its first day, and it has more than doubled in value since then. Its market value recently sat at $27 billion.

So what does the company do? In its own words, it's a "monitoring and security platform for cloud applications," which helps companies

enable digital transformation and cloud migration, drive collaboration among development, operations, security and business teams, accelerate time to market for applications, reduce time to problem resolution, secure applications and infrastructure, understand user behavior, and track key business metrics.

Various applications have been added to its platform over time, making it even more powerful and attractive to potential customers, and more will be added. Its customers appear to be finding a lot to like in Datadog's offerings, as the company's retention rate was recently around 130%, suggesting not only that it retained most customers, but also that they increased their spending.

Datadog is growing rapidly, with revenue tripling between fiscal 2018 and 2020. Like Zscaler, it's posting losses while it invests in growth -- developing additional technologies, hiring more people, acquiring more customers, and ramping up its capabilities. Despite that, it's generating free cash flow, which bodes well for its financial health.

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3. Palo Alto Networks

Palo Alto Networks (PANW 2.99%) is a global leader in cybersecurity, with a market value recently near $35 billion. Clearly, threats from cyberspace are not going away anytime soon, and companies can't afford to have their systems hacked into and their safeguards breached. Enter Palo Alto, with technology, programs, and even consulting services to help companies secure their data and workings.

In the company's last reported quarter, revenue and billings jumped 25% and 22% year over year, respectively, topping management's previous guidance. Its growth drivers include its cloud-delivered security subscription offerings, which have gone from four to eight in just two years, and the newer, higher support level that it's offering customers -- "Platinum Support."

Palo Alto's artificial-intelligence-powered threat detection platform Cortex counts 66% of the Fortune 100 among its customers, plus 35% of the Global 2000. Interestingly, the company notes that "Cortex XDR's Behavioral Threat Protection instantly blocked a SolarStorm attack on Palo Alto Networks" and it sees the SolarStorm attack as a growth driver, as it generated more than 1,000 assessment requests related to it. CEO Nikesh Arora noted in a conference call:

This will result in more awareness and focus on cybersecurity, which in all candor, is the need of the hour given the complete reliance on technology in these times. We expect that this attack will be a wake-up call to all enterprises to modernize cybersecurity and will serve as a net incremental tailwind, not just for us but also for the industry.

These three companies are not selling at bargain-basement prices. But each appears to have a rosy future ahead of it. Consider digging more deeply into any of the companies that interest you, and if you like what you think, you might start a position in one or more by buying a few initial shares, and then add to that position over time. Or play it more conservative and just add the companies to your watch list, hoping for a lower price in the future (and knowing that it may or may not materialize).

Remember, too, that there are plenty of other terrific growth stocks out there, and many of them are trading at lower valuations.