LIANGDUO, China — One crisp October morning, Han Youjun got into his silver delivery van and left this small town in eastern China. Within minutes, his van brimming with boxes of every size and shape, he was rumbling through rice paddies, down narrow village lanes and past modest farmhouses, deeper and deeper into China’s vast hinterland.

In the past, delivery drivers like Mr. Han would have had little reason to travel so far. China’s boom over the past four decades made its crowded metropolises wealthy. Much of the rest of the country, especially farming communities like those surrounding Liangduo, in the eastern province of Jiangsu, remained relatively poor.

But more and more, the benefits of China’s economic miracle are penetrating into smaller cities and countryside hamlets — as Mr. Han, a 32-year-old deliveryman for JD.com, an online retailer, knows all too well. The 70 packages crammed into his van that day were double the amount he usually hauled only 18 months earlier.

“The workdays have been getting longer,” he said.

China needs spenders in those places. The government is trying to shift the country’s growth engine away from its traditional dependence on factories and building things. Those old growth sources are no longer dependable and require more and more costly debt.