Application programming interfaces, or APIs, are essential building blocks of the online apps and connected services we use everyday. That’s why Microsoft’s venture arm M12 is leading a $25 million investment round for RapidAPI, a San Francisco-based startup that has built a popular API marketplace used by 1 million developers. Microsoft’s M12 lays out investment strategy, aims to make the corporate VC community more ‘founder-friendly’ RapidAPI helps developers find and connect to more than 10,000 publicly-available APIs. The 50-person company processes 500 billion API calls each month.