Unlike Amazon Web Services’ loosely coupled architecture, which consists of several essentially independent services that can optionally be tied together by developers, Google’s architecture is more unified but less flexible. For example, it is possible with Amazon to use their storage service S3 independently of any other services, while with Google using their BigTable service will require writing and deploying a Python script to their app servers, one that creates a web-accessible interface to BigTable.

What this all means: Google App Engine is designed for developers who want to run their entire application stack, soup to nuts, on Google resources. Amazon, by contrast, offers more of an a la carte offering with which developers can pick and choose what resources they want to use.

Developers simply upload their Python code to Google, launch the application, and can monitor usage and other metrics via a multi-platform desktop application.

More details from Google:

Today we’re announcing a preview release of Google App Engine, an application-hosting tool that developers can use to build scalable web apps on top of Google’s infrastructure. The goal is to make it easier for web developers to build and scale applications, instead of focusing on system administration and maintenance.

Leveraging Google App Engine, developers can:

• Write code once and deploy. Provisioning and configuring multiple machines for web serving and data storage can be expensive and time consuming. Google App Engine makes it easier to deploy web applications by dynamically providing computing resources as they are needed. Developers write the code, and Google App Engine takes care of the rest.
• Absorb spikes in traffic. When a web app surges in popularity, the sudden increase in traffic can be overwhelming for applications of all sizes, from startups to large companies that find themselves rearchitecting their databases and entire systems several times a year. With automatic replication and load balancing, Google App Engine makes it easier to scale from one user to one million by taking advantage of Bigtable and other components of Google’s scalable infrastructure.
• Easily integrate with other Google services. It’s unnecessary and inefficient for developers to write components like authentication and e-mail from scratch for each new application. Developers using Google App Engine can make use of built-in components and Google’s broader library of APIs that provide plug-and-play functionality for simple but important features.

Google App Engine: The Limitations

The service is launching in beta and has a number of limitations.

First, only the first 10,000 developers to sign up for the beta will be allowed to deploy applications.

The service is completely free during the beta period, but there are ceilings on usage. Applications cannot use more than 500 MB of total storage, 200 million megacycles/day CPU time, and 10 GB bandwidth (both ways) per day. We’re told this equates to about 5M pageviews/mo for the typical web app. After the beta period, those ceilings will be removed, but developers will need to pay for any overage. Google has not yet set pricing for the service.

One current limitation is a requirement that applications be written in Python, a popular scripting language for building modern web apps (Ruby and PHP are among others widely used). Google says that Python is just the first supported language, and that the entire infrastructure is designed to be language neutral. Google’s initial focus on Python makes sense because they use Python internally as their scripting language (and they hired Python creator Guido van Rossum in 2005).

[Courtsey: TechCrunch]