Parse may not have as big a name as the others in this review, but it offers a solid collection of back-end services as well as libraries for accessing these services from all of the major and not-so-major platforms. Once you build your tables full of data on Parse's server, the info can be pushed and pulled from platforms ranging from iOS and Android to Unity and Xamarin. Parse is a fast way to build a back end that services apps running across all of these platforms.
The eight different libraries for the various clients are packages that bundle the data into JSON, ship it to the Parse servers, and unpack the result. They're glue wrappers for moving data around as JSON packets. You could accomplish most of this with many other stock libraries, but they wouldn't make authentication as easy.
The Parse push system targets the subset of platforms that support push notification: Android, iOS, Windows Phone, OS X, and Windows 8 desktops. Most of the work occurs outside of Parse because the different platforms require certificates and configuration, all of which is described in detail in the documentation. Once you jump through the hoops, you should be able to send notifications from any of the platforms and to anyone subscribed to a channel.
Parse's data browser lets you mind your Parse tables over the Web.
One of the nicer features is comprehensive user management that includes hooks for working with Facebook and Twitter. The user authenticates through Facebook or Twitter using OAuth, or you log in with a password set up for your app alone. The access for each object in the database can be controlled using a permissions matrix that's based on either the local Parse username or the Facebook name. This allows you to piggyback on Facebook authentication, something that can simplify your app. The Parse library handles the OAuth, something that can be maddening to write from scratch.
Despite all the pretty Web screens for browsing the data, working with Parse is surprisingly text-based. I edited the control logic in an editor and pushed it with a command line. Debugging was best handled with the log files and messages. Tracing the path through long functions isn't really possible without installing much of the code locally.
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