Sun Hongkai, the 40-year-old watermelon inspector. Screenshot of Zaker

As a popular summer fruit, watermelon is almost a household necessity in China. But do you know how to choose a high-quality watermelon with the right shape, sweetness and water?

In Xiayi county, Central China's Henan Province, the "hometown of watermelons in China," there are special watermelon inspectors who can "feel the pulse" of each watermelon about to be sold. In just seconds, they can accurately identify the quality of a watermelon.

Sun Hongkai, a 40-year-old inspector, says he tests at least 100,000 catties a day, and at his peak, he earns around 2,000 yuan($296) a day, and about 30,000 yuan to 40,000 a month. Now farmers can sell their produce more easily on e-commerce platforms and watermelon inspectors can ensure the quality of every watermelon bought by consumers.