When comparing AppFog vs Back4App, the Slant community recommends Back4App for most people. In the question“What are the best hosting services for Node.js apps?” Back4App is ranked 2nd while AppFog is ranked 4th. The most important reason people chose Back4App is:
The platform is reliable allow to scale up the applications running on it.
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Pros
Pro Allows multiple app instances
Limits are based on total memory allocation, you can allocate as much RAM as you want for each instance. Even the pricing is based on the total amount of RAM allocated, $0.04/GB.
Pro 24/7 live chat support
While it's true that AppFog may be relatively new and the online support is not very extensive, they offer 24/7 professional live chat support for any questions or problems you may have.
Pro Simple command-line deployment tool
AppFog has a simple command line utility to recursively push a directory to production
Pro Supports multiple data centers worldwide
AWS US, Europe, Asia, Rackspace, HP, Azure, and even Private Clouds.
Pro Open source
Back4app is an open source BAAS and Backend generator.
Pro Smooth migration from Parse
Back4App offers a smooth migration for all former Parse users who wish to migrate their data now that Parse has announced that it will stop soon.
Cons
Con Slow deployment
The deployment process with AppFog is generally nice and easy because of its CLI. Unofrtunately the only downside of that process is the fact that it takes too long. A deployment to AppFog genereally takes up to 40 seconds, which should be fine if you are deploying once a week, but when you deploy every hour it starts bothering you too much.
Con Uses MongoDB for the backend, which is not considered very safe by many
Back4App uses MongoDB as the database where data is stored. Mongo has been known to have issues with data corruption and data loss.