Is the rapid urban growth beneficial or harmful for developing democratic government in third world

Basically how has rapid urban growth impacted the democratic development.

It is impossible to provide one answer that would describe all third world countries. The answer depends on how the legislative districts are apportioned and they aren't the same throughout the third world.

Highly populated areas tend to vote for socialized programs and rural areas for self reliance, i.e. less government intervention and control. Without any other apportionment vehicle, rapid urban growth would tend to force government toward socialized, centrally controlled systems which would make it easier for the defeat of democracy.

In the Unites States, our Congress has 1 Represenative per ten thousand population and 2 Senators from each state. If all of the representation was based on population, 5 or 6 of the largest urban areas would control the government and the areas that provide the food and many of the necessary products for the urban areas would have no control at all. Having the Senate apportioned by area created a balance in the U.S. But all third world countries don't work that way.

My answer would be urban growth works against democracy in countries where the legislature is apportioned by population only and in favor of it in countries that have a vehicle to balance rural and urban interests. Whether or not that's beneficial depends on your point of view.