Blank Street has a simple business: It sells coffee—sometimes in carts, usually in small stores. It launched its first location 17 months ago, before it began dotting Manhattan and Brooklyn with baristas.

Even a couple of years ago, a rapidly growing chain of no-frills, low-cost coffee shops might have had trouble finding interest from tech investors. But in today’s booming market for early-stage startups, the New York-based company has received commitments for its third funding round in a year. The $35 million investment comes just three months after the still-fledgling company received $25 million, said Vinay Menda, Blank Street’s chief executive.