It took 31-year-old Sneha Marathe half a day to book an appointment online for a Covid vaccine.

"It was a game of 'fastest finger first'," she says. "The slots filled up in three seconds." But the hospital cancelled her slot at the last minute: they had no vaccines. Ms Marathe went back to try for another appointment.

All 18-44 year-olds in India have to register on the government's CoWin platform to get vaccinated. With demand for jabs far outstripping supply, tech-savvy Indians are even writing code to corner elusive appointments.

Ms Marathe can't code, but she is among millions of Indians who are on the right side of the country's digital divide - unlike hundreds of millions of others who don't have access to smartphones or the internet, currently the only route to a jab.

Prime Minister Narendra Modi's federal government has opened up vaccinations for some 960 million eligible Indians without having anything close to the required supply - more than 1.8 billion doses.

Worse, the severe shortage comes amid a deadly second Covid wave and warnings of an impending third wave.