The brightest lights of tomorrow are often just a dim glow today. The current crop of tech titans were also small and easily overlooked once upon a time. Now, they are looking over their shoulders as the next generation shapes up to challenge the old winners.

In fact, the world's largest providers of digital services are spending billions of dollars around the globe to stay ahead of the disruptors. If you're betting on online companies stealing market share in utterly traditional industries, here are two stocks you should consider buying now.

Duolingo: The enterprising educator

Online educator Duolingo (DUOL 1.74%) has much bigger plans than dominating the language-learning space it is exploring today. Many years down the road, the grand ambition is to provide world-class education to anybody with a smartphone, on many different subjects.

This is no secret. Duolingo's investor relations site, regulatory filings, and press releases all flaunt the company's mission statement -- often in extra-large letters on the first page: "Our mission is to develop the best education in the world and make it universally available."

The language-teaching opportunity is certainly robust enough to serve as a powerful rocket booster in Duolingo's early years. Management estimates consumers spend about $61 billion annually on learning new languages, and Duolingo has only captured a $339 million slice of that business opportunity so far. That's about 0.5% of the addressable market -- a vanishingly small sliver of a massive market.

The company is making inroads fast, though. Trailing sales increased by 50% over the last four quarters, and Duolingo is achieving this hypergrowth while also pocketing 9% of the incoming revenue in the form of free cash flows:

DUOL Revenue (TTM) Chart

DUOL Revenue (TTM) data by YCharts

Despite the robust cash profits, skyrocketing sales, and enormous addressable market, Duolingo's stock has taken a beating recently. Share prices are down by 49% over the last year. I picked up some shares on several occasions over the summer and may do it again before the end of the year. This stock is a screaming buy right now.

Fiverr: The productivity pioneer

I have also been buying more Fiverr International (FVRR 0.12%) stock recently, and the stock looks even more tempting today.

Like Duolingo, this freelance services wrangler has suffered dramatic share price cuts during the inflation-based flight from growth stocks. Fiverr's share price has plunged 78% lower in 52 weeks, and the stock is back where it was in the spring of 2020. Looking at the stock chart, you might jump to the conclusion that Fiverr enjoyed a golden age during the early days of the coronavirus health crisis, and that growth engines are all out of fuel by now.

Well, that's not what I see. Fiverr's trailing sales are still surging higher, including a 22% year-over-year jump in the recently reported third quarter of 2022. And, just like Duolingo, Fiverr is collecting this revenue with a healthy cash profit. Free cash flows added up to $26 million over the last year, which works out to a 7.7% cash-flow margin.

FVRR Revenue (TTM) Chart

FVRR Revenue (TTM) data by YCharts

Based on the current mix of mostly digital freelancing services you can find on the Fiverr platform today, management estimates its addressable market to be worth approximately $115 billion per year. That's only the U.S. market, not a global tally. Maybe it's time to update that market estimate, because Fiverr is already exploring international markets in seven languages.

At best, Fiverr has secured a 0.3% of just the American market opportunity, leaving vast tracts of unexplored opportunity.

Both Fiverr and Duolingo run exciting high-growth businesses aimed at enormous target markets. Don't forget that these companies are profitable on a cash-flow basis, which insulates them from the interest rate turmoil in the current economy.

Picking up some of their shares at the inflation-boosted discounts of November 2022 should set you up to make a lot of money in the long run.