When Google's AppEngine first debuted, it was all about Python. A year after launching, Google decided to expand to Java, though there has always been a gap between the two languages.

The new AppEngine 1.4.3 is an attempt by Google to bring the Python and Java runtimes closer to parity.

For Python users, they now get a Testbed Unit Test Framework which is similar in function to the Java Testing Framework already in AppEngine.

For Java users, they now get the benefit of concurrent requests.

"Until now, Java applications relied on starting additional instances to dynamically scale up for higher traffic levels," Greg D'alesandre from Google's App Engine Team wrote in a blog post." Now with support for concurrent requests, each application instance may serve multiple user requests at the same time."

Concurrency is a critical feature for any type of cloud deployment. It's an area that AppEngine has been steadily improving over the last year or more. The AppEngine 1.3.6 update for example added multi-tenancy support.

Another key new feature in AppEngine 1.4.3 is something called, Prospective Search. According to Google, Prospective Search will enable developers to build services that function like Google Alerts.