Requests are piling up from enthusiastic programmers using the App Engine hosted application development environment,

again testing Google's ability to meet the expectations of external developers, a demanding bunch that the company considers key to its success.

Excited about the service, developers are eager for Google to move fast and add basic features they need to launch commercial applications.

Some popular requests: removing the resources ceiling so that they can purchase additional computing capacity; support for more languages beyond Python; and securing application communications via, for example, SSL and HTTPS.

Google App Engine product managers Pete Koomen and Paul McDonald are aware of these and other commonly requested features for App Engine, but, following Google's policy, are reluctant to disclose detailed development and rollout plans.

However, they say they are encouraged by the level of interest and engagement developers are showing for App Engine, as evidenced by their active participation in the service's official discussion forum and in a wish-list page Google set up, which contains requests for more than 400 features and enhancements.

"We're seeing a lot of great things built on App Engine and have gotten great feedback from developers," McDonald said in a phone interview.

Google's App Engine team is listening closely to developers' requests and is actively working on improving and extending the service, he said. "We have great things in the pipeline," McDonald said.

App Engine was introduced in limited availability in early April and opened up widely in late May.

The initial 10,000 free App Engine accounts that Google offered got snapped up very quickly. By the end of May, when Google opened up the service to anyone, the company disclosed that it already had let in about 75,000 developers, and that another 80,000 were on the waiting list.

Although Google doesn't disclose how many App Engine accounts have been opened, it's safe to estimate that by now there must be well over 200,000, said Gartner analyst Ray Valdes.

"That's a lot," he said. "Now Google has to fulfill App Engine's value proposition: that developers write code and Google handles everything else."

App Engine isn't designed to be a generalized "cloud" computing infrastructure and development environment for all types of applications and developers.

Instead, App Engine is for applications of the sort Google develops: Web applications with mass appeal that don't require long-running processes to, for example, crunch scientific data. App Engine is designed instead for database-backed Web applications like blogs, office productivity programs and social-networking wares.

Unlike other hosted computing and development services, like Amazon's AWS, App Engine provides a highly integrated set of components, reducing the amount of tuning and configuring that developers must engage in.

This design sacrifices flexibility and control by reducing options, but is in line with App Engine's ultimate goal of appealing to developers who want to create and deploy their application quickly, and are happy to have Google handle the rest.

The App Engine design has clearly struck a chord, and it's clear Google now has its hands full, given the service's popularity.

In e-mail interviews with App Engine developers, two things became clear: They are very enthusiastic about the service and they are eager for Google to enhance and expand it.

Some of the most common pluses mentioned by App Engine developers are its automated load balancing; its highly scalable, Google-designed data store, file system and query language; its tight component integration; and overall simplicity.

Bill Katz, a Palo Alto, California, web entrepreneur and developer, already wrote an application called Bloog, which he released under an open-source license, and is working on developing two other applications.

Since his team is made up of just himself and his wife, he values App Engine's integration, automation and simplicity.

"App Engine removes a number of tasks I'd have to handle for a very scalable web app, like maintaining multiple servers [and] a scalable database," he said.

He finds Amazon AWS "great" -- he uses its S3 service for his personal backup storage and