Astonishing data for 2021 tell the story. U.S. start-ups raised $330 billion, nearly double 2020’s record haul of $167 billion, according to PitchBook, which tracks private financing. More tech start-ups crossed the $1 billion valuation threshold than in the previous five years combined. The median amount of money raised for very young start-ups taking on their first major round of funding grew 30 percent, according to Crunchbase. And the value of start-up exits — a sale or public offering — spiked to $774 billion, nearly tripling the prior year’s returns, according to PitchBook.

The big-money headlines have carried into this year. Over a few days this month, three private start-ups hit eye-popping valuations: Miro, a digital whiteboard company, was valued at $17.75 billion; Checkout.com, a payments company, was valued at $40 billion; and OpenSea, a 90-person start-up that lets people buy and sell nonfungible tokens, known as NFTs, was valued at $13.3 billion.

Investors announced big hauls, too. Andreessen Horowitz, a venture capital firm, said it had raised $9 billion in new funds. Khosla Ventures and Kleiner Perkins, two other venture firms, each raised nearly $2 billion.

The good times have been so good that warnings of a pullback inevitably bubble up. Rising interest rates, expected later this year, and uncertainty over the Omicron variant of the coronavirus have deflated tech stock prices. Shares of start-ups that went public through special purpose acquisition vehicles last year have slumped. One of the first start-up initial public offerings expected this year was postponed by Justworks, a provider of human resources software, which cited market conditions. The price of Bitcoin has sunk nearly 40 percent since its peak in November.

But start-up investors said that had not yet affected funding for private companies. “I don’t know if I’ve ever seen a more competitive market,” said Ambar Bhattacharyya, an investor at Maverick Ventures.

Even if things slow down momentarily, investors said, the big picture looks the same. Past moments of outrageous deal making — from Facebook’s acquisitions of Instagram and WhatsApp to the soaring private market valuations of start-ups like Uber and WeWork — have prompted heated debates about a tech bubble for the last decade. Each time, Mr. Bahat said, he thought the frenzy would eventually return to normal.

Instead, he said, “every single time it’s become the new normal.”

Investors and founders have adopted a seize-the-day mentality, believing the pandemic created a once-in-a-lifetime opportunity to shake things up. Phil Libin, an entrepreneur and investor, said the pandemic had changed every aspect of society so much that start-ups were accomplishing five years of progress in one year.