It's legacy technology. MongoDB is basically the same thing under the hood, and more "standard".

MongoDB is from 2009, while FoundationDB 2013, so wouldn't the notion of legacy be the reverse of what you wrote?

	▲	otabdeveloper4 5 hours ago \| parent [-]
		"Legacy" isn't about age, it's about adoption speed. ("Legacy" products have a negative growth rate.)