Google faces several major Android-related headaches. First, while Google makes most of its revenue from advertising, Android has so far been an ad dud compared with Apple’s iOS, whose users tend to have more money and spend a lot more time on their phones (and are, thus, more valuable to advertisers). Because Google pays billions to Apple to make its search engine the default search provider for iOS devices, the company collects much more from ads placed on Apple devices than from ads on Android devices. A recent analysis by Goldman Sachs estimated that Google collected about $11.8 billion on mobile search ads in 2014, with about 75 percent coming from ads on iPhones and iPads.

A brighter spot for Google is the revenue it collects from sales via Android’s app store, called Google Play. For years, Android apps were a backwater, but sales have picked up lately. In 2014, Google Play sold about $10 billion in apps, of which Google kept about $3 billion (the rest was paid out to developers). Apple makes more from its App Store. Sales there exceeded $14 billion in 2014, and rising iPhone sales in China have led to a growing app haul for Apple. Still, Google’s app revenue is becoming an increasingly meaningful piece of its overall business, and it is also growing rapidly.

Google is investing heavily to make sure that continues. Purnima Kochikar, business development director for Google Play, told me her team supporting Android app makers grew “by 15 times” in the last two and a half years. She added that even if hot Silicon Valley start-ups still create apps for iOS first, app makers in other parts of the world see Android as a surer path to the masses. “The reality is that folks like you should play a role in educating the Silicon Valley,” she said.

But how long Google can expect Play to keep paying remains an open question, thanks to the second Android-related headache. Google’s strategy of giving Android to phone makers free has led to a surge of new entrants in the phone business, several of which sell high-quality phones for cut-rate prices. Among those is Xiaomi, a Chinese start-up making phones that have become some of the most popular devices in China.

Because Xiaomi and others don’t make much of a profit by selling phones, they’re all looking for other ways to make money — and for many, the obvious business is in apps offering mail, messaging and other services that compete with Google’s own moneymaking apps.