SEOUL, South Korea — The small white delivery trucks zip down streets all over South Korea. The uniformed workers send photos of safely delivered packages to impatient customers. Workers can move so fast, their employer promises, that it calls the service “rocket delivery.”

The trucks and the operation belong to Coupang, a start-up founded by a Harvard Business School dropout that has shaken up shopping in South Korea, an industry long dominated by huge, button-down conglomerates. In a country where people are obsessed with “ppalli ppalli,” or getting things done quickly, Coupang has become a household name by offering “next-day” and even “same-day” and “dawn” delivery of groceries and millions of other items at no extra charge.

The company, which is sometimes called the Amazon of South Korea, is set to get a big endorsement on Thursday from Wall Street. Its shares are expected to begin trading in an initial public offering that will raise $4.2 billion and value the company at about $60 billion, the second-largest American tally for an Asian company after Alibaba Group of China in 2014. On Wednesday its shares were priced at $35, according to a person close to the company.

Coupang may need the money. South Korea’s big conglomerates, called chaebol, and others are building their own delivery networks as Coupang plans its expansion. It faces other issues, too, such as growing concerns about working conditions after the death of several Coupang warehouse and delivery workers that some relatives and labor activists blamed on overwork and poor labor practices.