There’s no question Google’s foray into delivering goods to homes and offices, called Google Shopping Express, has been a hit with online shoppers who have tried it. But GSX, as it’s known inside of Google, remains in a precarious position even as it gets more funding and expands beyond the San Francisco Bay Area, New York and Los Angeles.

In one of the biggest efforts to rival Amazon.com’s quick-shipping services, Google launched GSX 16 months ago by aligning itself with brick-and-mortar retailers that are eager to counter their e-commerce nemesis. But inside and outside of Google, there are open questions about the commitment of some retailers, including key partner Target.

Even more troublesome for Google: the cost structure of GSX is still far from where it needs to be for the service to be profitable, according to people who have been involved in its finances or were briefed about it.