Google's Play Store finally has its very first app with five billion downloads, and that title unsurprisingly goes to Google Play Services. The Google Play Services framework is required to use most Google-made apps aside from the actual Play Store, along with any apps that use certain solutions from the company such as the Maps API, Google+, and Google Wallet. The Google Play Services app is the front for that framework; the download contains the framework, and the app itself installs the framework and handles interactions with it internally. It has no user-accessible interface, meaning that the title of the first user-facing Android app with five billion downloads is still up for grabs.
Due to the way the Play Store operates, the app's download range won't be updated again until it reaches ten billion downloads. Google Play Services was last updated on July 10, bringing it up to the version 11.0.4. The update included fixes for apps that use Google's Firebase cloud framework, changes to how in-app advertising is handled, and tweaks for APIs used in Google Play Games and other services. Recently, the version 11 update family for Google Play Services, having started its rollout back in May, introduced full compatibility for Android Instant Apps.
Using Google Play Services rather than integrating such functionality into APIs for use by developers on a per-app basis is arguably a far more favorable approach to integration between third-party apps and Google's software solutions, but many users on the Play Store complain about the size of the app, how ubiquitous it is, issues with updating it, and other problems. Mostly, the app poses a problem for some legacy devices with extremely small amounts of RAM and storage, some of which are either unable to install many or any apps after installing Google Play Services, or are unable to install the software at all. The size of the app can vary between Android versions and devices, but averages around 80MB. Even with the issues it can pose for legacy devices, it has served as a very effective integration tool from Android's inception, and Google will likely keep it that way for the foreseeable future.