In the early morning of April 2, as Josh Silverman started his workday, the Etsy chief executive was amazed to see a sudden surge in traffic to the handcraft e-commerce site on a run-of-the-mill Thursday.

One thing in particular was driving traffic: Searches for "face masks" rose 100-fold in a matter of hours that morning, hitting nine searches a second at one point.

While Etsy's sellers had been offering face masks for several weeks since the start of the COVID-19 pandemic, media reports surfaced that morning suggesting that the U.S. government was going to change its stance and recommend Americans wear face masks in public settings to help contain the spread.

"It happened like an explosion. It was instant," Silverman tells Fortune. Some sellers were moving the entire previous month's orders in just an hour. But the surge in searches didn't come without challenges.

For one thing, he wanted to be sure that sellers could fill those orders, lest it lead to a bad experience for someone new to the site, losing Etsy a chance to make a good first impression.

What's more, when Silverman typed “face masks” into the search engine, results were yielding a lot of Halloween masks and other irrelevant products. "That’s not what anyone thinks of as face masks in this moment," he says.

By 8:30 a.m. that morning, he and his team were doing triage by hand of the top 5,000 top results, an immediate fixing of its algorithms. They placed vendors who really sold cloth face masks first in the ranking and redirected shoppers to the sites of sellers who confirmed they could handle the orders as a way to redistribute demand, thereby retraining its search engine.

Over the next 48 hours, Etsy recruited more sellers to make masks, helping them figure out how to get more fabric and set up their shops quickly. "In a short time, we stood up a midsize company within Etsy," says Silverman.

This was all much more labor intensive than how Etsy would normally operate. But the payoff was undeniable: In April, Etsy sold 12 million masks worth $133 million, or one-sixth of its monthly tally, and Silverman says demand is holding up well.

What's more, sales on the Etsy site of items other than masks rose 79% last month, despite a drop in wedding-themed gifts during what is normally a peak time for that category. Etsy was already doing well, though not quite that well: In the first quarter of 2020, sellers sold $1.35 billion worth of goods on its sites, up 32.2% from a year earlier.

A bonanza of new customers

There's an important, longer-term upside for Etsy: In April alone, it won over 4 million new customers and got back 2.5 million others who hadn't used the site in at least a year. (At the start of 2020, it had 46.4 million active buyers and 2.7 million sellers.)

Wall Street has noticed. Shares hit a 52-week low on March 16, coincidentally when the lockdown started in major cities like New York as investors worried about the coming economic downturn. But in the two months since, Etsy shares have risen 157%, making the company worth almost $10 billion.

Silverman admits he was not sure how people were going to behave as lockdowns began. But he thinks people wanting to support independent businesses and buy one-of-kind items—or at least those that are not mass-produced—has a lot to do with Etsy's success.

And the influx of new shoppers has been a rare opportunity for Etsy to wow new customers. "It was important that it be a good experience," says Silverman.

Initial data suggests many are sticking around: Some 32% of new customers who bought a mask last month bought another item within two weeks. And Silverman says on-time shipment statistics and call-center volume suggest the customer experience has been good.

Wall Street analysts seem to agree with the thesis that Etsy will hang on to its new customers once lockdowns end and other retailers reopen their stores. "Even for the existing buyers, they may be exposed to the variety and selection of products available, which could induce them to come to the platform and buy more than just once a year," Deutsche Bank analyst Kunal Madhukar wrote in a research note.

Since Silverman took the helm three years ago, he has sought to professionalize a site that often felt like a flea market. That has included vastly improving its search function—something he says is hard, considering that Etsy sells 60 million unique items at any given time. And occasionally it has meant friction with sellers, either from higher fees or pushing them to offer fast shipping.

But at a time when eBay has floundered and “re-commerce” sites are on the rise, Etsy wants to take advantage of every chance it gets to attract new customers who might not have thought of it much, especially as shopping behavior is in flux.

"For anything you need, the habit for so many people is Amazon, Amazon, Amazon," Silverman says. "If I could just get them to pause for a split second and think to themselves, 'Where else could I get something similar?,' Etsy is going to come to mind a lot of the time."

And millions of mask buyers are now at least more aware of Etsy.