LONDON — For months, Gabrielle Walker had been looking for a part-time job. She applied to restaurant chains and retailers like Nando’s and Primark, and she scoured the job search site Indeed.

Nothing.

Then one day, Walker, a 19-year-old student at University College London, was scrolling through TikTok and stumbled on a video about an app called Stint. A face on the screen explained that Stint could help students earn money by working brief temporary stints at places like restaurants and bars that require little training or experience.

Walker downloaded the app, took a 15-minute intro course and days later snagged a job polishing cutlery at a Michelin-star restaurant in London — for one day. Between May and June, she took on several other gigs, squeezing them into her class schedule where she could.

“Everyone could do it,” Walker said.

Stint, in use across the U.K., has grown in popularity, alongside similar apps in the United States like Instaworks and Gigpro, as one response to the peculiar ways in which economies have been rebounding from the pandemic recession. Uncertainty about the durability of the recoveries and the tentative re-openings of businesses still threatened by the coronavirus have made flexibility a top priority — for workers and employees alike.

As the hospitality industry, in particular, confronts worker shortages, these apps are helping form an ultra-short-term worker-employee relationship, something that hasn’t widely existed in recent decades. Walker noted that even students with no relevant experience could sign up with one of these apps and likely find paid work — as brief as a couple of hours — that fits their schedule from week to week.

In contrast to Stint, Instaworks and Gigpro are suited more for skilled or experienced workers who want or need short-term shifts. Collectively, the newer apps represent a variation on the many gig apps that sprang up in recent years — from Uber and DoorDash to TaskRabbit and Thumbtack — that typically serve households in need of a one-time service. What distinguishes the latest apps is that they link workers with employers that have a steady need for labor but don’t necessarily want to commit to permanent hires given the uncertainties from the pandemic.

“It’s no surprise that during COVID, when everything became virtual that these … marketplaces might have exploded,” said Fiona Greig, co-president of the JPMorgan Chase Institute, a global financial thinktank, whose research expertise includes the online platform economy.

The newer gig apps could potentially help ease the labor shortage in England, where nearly all pandemic restrictions were lifted last month. Most recently, its “ pingdemic” — by which the National Health Service alerted people to self-isolate if they had been in close proximity to someone who had tested positive for the virus — disrupted businesses. Many workers had to isolate themselves, and some stores had to shut down temporarily for lack of labor.

“Gig economy workers can help plug the gap,” said Mariano Mamertino, a senior economist at LinkedIn.

While Mamertino holds out hope that pandemic-related shortages will ease as England’s economy reopens and vaccine rollouts continue, “one question mark that remains for the UK,” he said, “is whether firms will have to permanently adapt to a new post-Brexit status quo.”

Not everyone is celebrating the trend. UKHospitality, the leading trade association for Britain’s hospitality sector, suggested that while businesses are used to innovating, the economic forces that have created staff shortages in the industry could pose enduring problems.

The association, along with the British Beer and Pub Association and the British Institute of Innkeeping, asserted that the road to recovery requires that the government “put in place the right trading environment,” including an expansion of business tax cuts. UKHospitality has also urged an overhaul of post-Brexit visa rules to make it easier for foreigners to work in the industry.

Sol Schlagman, who co-founded Stint along with his brother, Sam, drew from his own experience as a college student in creating it.

“It’s the student that needs to have money to pay their rent,” he said, “but it’s also the student that wants to buy a pair of shoes they wouldn’t necessarily buy otherwise.”

The restaurant chain Chipotle uses Stint to recruit workers “at short notice to cover peak times in our restaurants,” said Jacob Sumner, its director of European operations. Chilango, another food chain, said its stores use the app when they need “extra pairs of hands during busy times.”

The use of apps to connect businesses and workers for short-term gig work appears to be a growing trend in the United States as well.

“The biggest change we see is this desire for flexible staffing on both sides,” said Sumir Meghani, CEO and co-founder of Instaworks, which connects businesses with temporary or short-term hourly workers.

During the pandemic, Meghani said, businesses discovered that the rise and fall of viral cases — and the resulting disruptions to their operations — sometimes require them to scale up or down at any given notice.

Greater flexibility in the worker-employer relationship during the pandemic period is also what Gigpro’s founder, Ben Ellsworth, has observed. His app, which operates in three Southern U.S. states, is expanding, to try to address staffing shortages exacerbated by the pandemic.

Ellsworth, who spent years in the restaurant industry, said that with eateries in particular, workers have been “plagued with low wages, lack of incentive, no real focus on flexibility or quality of life.” Stuck at home after being laid off, many of these workers either turned to other industries, Ellsworth suggested, or came to recognize gig work as an opportunity to tailor their work hours to their own needs. That realization arrived just as businesses, too, sought workers to fill part-time hourly slots — at least temporarily — as business restrictions eased.

“Now that restrictions have been lifted and businesses are starting to boom again,” Ellsworth said, “they’re getting stretched.”

While the flexibility provided by these apps serves a need now, some critics foresee a threat to workers over the long run. If gig workers replace jobs formerly filled by permanent restaurant or retail employees, they could diminish job security, along with sick pay and other benefits.

“The flexibility of the gig economy may be welcome when crises take out regular staff, but this comes at a potential cost to society,” said Ann Light, a professor of design and creative technology at the University of Sussex.

Still, Greig acknowledged that the apps can lower barriers to entry for people who need cash quickly, a category that includes many young workers with limited work experience.

The role of gig workers, for employment purposes, can vary widely with these apps. Student users of Stint are employed as workers, guaranteed a set wage and accrued holiday pay. On the other hand, those who use Instaworks are considered independent workers who can choose to be either contractors or employees. Gigpro users are independent contractors.

Platforms also take their cue from an international perspective, Light suggested, even as they battle local jurisdictions. This year, Uber drivers in Britain won rights as workers. Similarly, last week, a judge struck down a California measure that exempted app-based ride and delivery services like Uber from a state law requiring that drivers be classified as employees eligible for benefits.

In the meantime, the worker apps appear to be filling a niche. For Monty Jackson, a student at the University of Plymouth in England, the work gigs he’s obtained through Stint have helped fund his swimming hobby.

He had been working part time at restaurants and bars. But the work shifts he received had interfered with his studies. Now, he plugs in only the hours when he’s available and picks up a work slot sometimes the same day he looks for one.

“The flexibility attracted me,” Jackson said.