BENGALURU: India has added new customers at the fastest rate for Amazon in its history of operations in multiple countries, the company's head of international consumer business Diego Piacentini , told TOI.India is also the second biggest investment country for the company after the US, he said, adding that India was key to Amazon's future success.Piacentini, who reports to founder Jeff Bezos and is the highest paid executive in the company, said he would be surprised if India was not the second biggest country for Amazon after the US over the next 10 years, given the pace at which it was growing. The India operations grew by 500 per cent in the number of units shipped last year."I am an optimistic person but my optimism was not enough. If you told me 27 months back that I am going to sit here and look back at a growth of 500 per cent, year-on-year, I would have said that is not possible," said Piacentini.Amazon's Indian operations were launched just a little over two years ago and the company has been gaining market share over rivals. Some estimate it is already second to Flipkart , and ahead of Snapdeal and Paytm. Last year, Bezos had announced that the company has earmarked more than $2 billion in funds for investments in India."We need to look at the long term. The kind of massive infrastructure and partnerships we are building in this country is huge. The US and Europe after some point will have a different growth trajectory," Piacentini said.While bullish on the mobile platform, which accounts for 65 per cent of its traffic, the company said it would serve customers on all platforms, even as it thinks app-first. Rival Flipkart has said it will move to an app-only strategy; its subsidiary Myntra has already become app-only. But Amazon indicated that such a move would be misguided.