Helps you cloud-enable your mobile apps in minutes

Let us handle the complicated backend while you focus on your application

LeanEngine is an open source project aiming at making the development of cloud-enabled mobile applications really simple, fast and fun. It consists of a pre-configured Google App Engine server and client libraries for mobile clients. It lets you focus on developing your mobile app while it handles all the boring and complicated stuff. Stuff like:

  • logins (Facebook, Google, Twitter, OpenID)
  • saving data to the cloud
  • querying data from the cloud
  • security

All this you can achieve with using LeanEngine libraries and a few lines of code on your clients. Not only that. Because it runs on your own instance of App Engine you keep total control of the data.

Take a look at these examples to get a feeling how simple it really is. After including the LeanEngine client library in your project tasks like saving data to the cloud become a matter of only a few lines of code.
LeanEntity catEntity = LeanEntity.init("cat");
catEntity.put("name", "Mookie");
LeanQuery query = new LeanQuery("cat");
query.addFilter("age", LeanQuery.FilterOperator.GREATER_THAN_OR_EQUAL, 2);
query.addSort("age", LeanQuery.SortDirection.ASCENDING);

LeanEntity[] result = new LeanEntity[0];
try {
    result = query.fetch();
} catch (LeanException e) {
    // alert user something went wrong
try {
    LeanEntity.delete("cat", entitiyID);
} catch (LeanException e) {
    // alert user something went wrong

There are two parts of LeanEngine - server and client(s).


Server part runs on Google App Engine. The good news is you really don't need to do any development on the server part. We have included all the functionality we think you might need. The code is open source and very well documented, so in case you do need some special feature, you can add it yourself. Or ask for our help if you don't feel comfortable messing with it yourself.


All you need to do on the client side is to include the LeanEngine library in your project and you are ready to go. To make things even simpler we provide a sample project to get you started as fast as possible. The documentation includes example code for most common tasks.


Here you can get the LeanEngine Server. To run it you must also have the Google App Engine SDK.

Server on GitHub »

Currently v0.8


Here you will find client libraries and an example Android project. For a real fast and painless start we recommend you start with the example app.

Android on GitHub »

Currently v0.8


iOS client libraries and example app.

iOS on GitHub »

We would love to hear from you. Please give us your feedback. Tell us what you have built using LeanEngine. If you would like to suggest a feature you are missing, have an idea how to make LeanEngine better, report a bug, ask for help,... write us at and we will get back to you.

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How much does it cost?
LeanEngine is free and open source.
What does the server run on?
Server runs on Google App Engine. We suggest you run the server locally during the development.
I don't know anything about server or cloud development. Is LeanEngine for me?
It is exactly for you! We have included all the basic functionality we think you might need so there are good chances you will not need to do any development on the server part.
I am stuck. Can you help me?
Yes. Contact us and we will try to resolve your issues.
I am running the server locally. It is accessible from http://localohost:8080 but not from other devices on the same LAN.
You need to add "-a" to Server parameters.
I have successfully deployed the server but the login with Facebook or Google does not work.
You have probably forgotten to enter your Facebook "secret" and enable login vith openID. Check the Quickstart guide on how to do this
Do you plan to support WP7?
Yes, in the future. If you would like to contribute you are welcome.