On-demand delivery service Postmates has launched in Washington, D.C. today, marking its fifth market in the U.S. The company is also releasing a beta version of its app for Android, which will make the service available for a whole new group of mobile users.

It’s hard to believe it’s been two years since Postmates first launched service in San Francisco. It spent a lot of time in its home market working out the kinks, improving its app, and proving out a model that would allow customers to get items delivered within an hour for a low price.

Then after a while it started expanding into other markets where people need stuff delivered for cheap in under an hour, places like Seattle and New York City and Brooklyn.

That expansion has gone really well, according to Postmates co-founder and CEO Bastian Lehmann, especially in the Big Apple. Manhattan, where Postmates has been in business for the last six months, has grown three times faster than San Francisco and is already profitable, Lehmann says.

So it shouldn’t be a surprise that we’d hear about another new Postmates market not long after. With its expansion into Washington, D.C., Postmates seeks to meet existing demand in the nation’s capital. According to Lehmann, D.C. has had the highest number of app activations outside of New York City.

There are a number of things that make Washington, D.C. an attractive market: It’s densely populated, has a great food scene, and has a lot of office workers with expense accounts who get stuck at their desks during lunch.

While Postmates sent in an advance team to recruit couriers, the company plans to manage the new market from New York, thanks to the proximity of the two cities. And it’s been busy populating its app with restaurants and shops and menus from the area.

In addition to a new market, Postmates is close to releasing a new app for Android mobile users. For now, that app is only being launched in beta at postmates.com/android rather than through the Google Play store.

Part of the reason for the limited release is that the company’s biggest concern is seeing overwhelming demand due to a large number of new Android users. “It’s such a highly requested feature we don’t know what to expect,” Lehmann said.

While “too much demand” seems like a good problem to have, Postmates has already been having problems keeping up with the number of requests it’s had coming in. Last month it introduced “Blitz pricing,” which is kind of like Uber’s surge pricing, and is its own way of dealing with high demand.

Postmate investors include Founders Fund, SoftTech VC, Matrix Partners, Crosslink Capital, and Expansion Venture Capital, along with angels such as David Sacks, Dave Morin, Bill Lee, Scott Banister, David Wu, Thomas Korte, Naval Ravikant, Russell Cook, Russel Simmons, Walter Lee, Andy McLoughlin, Paige Craig, Jawed Karim.