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.