China's booming e-commerce has led to a rising number of parcels, with the country's express delivery sector having handled 50.7 billion parcels last year, an annual increase of 26.6 percent, according to the State Post Bureau. Meanwhile, the sector generated revenue of 603.8 billion yuan ($90 billion), up 21.8 percent year-on-year.

For Ge, transporting parcels on the Qinghai-Tibet Plateau is no easy job. The route passes through one of the most hostile places on Earth, with the atmosphere having just 43 percent of the oxygen found on the plains.

The annual average temperature is -6 C, and the average number of days with strong gales is 168.

But perhaps the most difficult part of Ge's journey is a 100-meter-high mountain ladder known as the "Sky Ladder". "I still remember carrying a 10-kilogram parcel while climbing up the ladder in -15 C, and all I could hear was my heavy breathing," Ge said.

"Eight years ago, I climbed up the ladder for the first time. I felt dizzy halfway up, and I had to rest frequently to finish my journey."

Bao Junfeng, from China Post's Golmud branch, said, "The route is probably the world's longest and highest rural route for deliveries."

Due to years of work at high altitude, Ge's lips look purple. Frequent attacks of altitude stress, influenza and inflammation have caused him to lose three of his teeth.

Last year, the company organized a medical examination for the couriers, and Ge was diagnosed with two kidney stones. "My family was nervous about my health and urged me to go for an operation, but I was so attached to my job that I just couldn't make time for it," he said.