For all the turmoil these days, the U.S. stock market remains extremely attractive to investors around the world, simply because of its sheer size and liquidity. But it’s still quite difficult for investors in other parts of the globe to trade stocks on U.S. exchanges. A San Mateo-based startup called Alpaca has quietly capitalized on that opportunity by offering an API to financial services firms that let them sell trading services to their consumer user bases.
Today, Alpaca claims it serves more than 5 million brokerage accounts, and has more…