The marathon vote in India: More than 900 million people are eligible to vote.

More than 8,000 candidates are vying for a seat in the lower house and polling lasts for nearly six weeks or 39 days to be exact.

So, needless to say an election in the second-most populous country on earth is complicated and elaborate.

India has four times as many registered voters than the United States.

And it has higher voter turnout than the U.S.

That's because the country's committed to polling every one of their voters.

And when I say committed,

I mean, they're required by law to do it.

Election rules say that there has to be a polling station within two kilometers of every dwelling.

That's true for the more than 20 million people that live in Mumbai.

And for the sole human living in Gir Forest National Park in Gujarat, who gets his own polling booth.

So in practice, that's one million polling stations and 12 million polling officials.

These election workers go to all edges of the country — literally:

700 special trains will be deployed this year

as well as boats, planes, elephants and teams of camels.

I did say elaborate didn't I? Key to this entire exercise is this contraption.

India has been using secure electronic voting machines for two decades.

Each machine has three parts.

First, there's the control unit that counts and stores the votes.

And there's the balloting units, where voters pick their candidates by pressing a button.

The third piece is a secure printer that deposits a hard copy of each ballot into a sealed box.

And it's just that simple.

The electronic voting process has made it dramatically easier for Indians to cast votes.

But it's also part of the reason why the process takes so long.

There are just 1.6 million control units,

but more than 900 million eligible voters.

That's roughly one unit for every 552 voters.

So, what's at stake?

Voters are choosing who will fill 543 seats in Parliament's lower house, the Lok Sabha.

The golden number is 272 seats.

That's how much a party or coalition needs to pick the next prime minister.

Then in five years, people start this process all over again.