They haven’t let us look under the hood, but Google yesterday published a few more specs about App Engine, including how usage will be priced if an application deployed using its infrastructure exceeds the limits set for the free edition.

When it launched the service in early April, Google had set a rather generous limit of 5 million page views per month, but didn’t disclose pricing or policies about overages. Now it says that successful applications will be subject to these fees:

  • CPU time - US$0.10 - $0.12 per core-hour
  • Storage - $0.15 - $0.18 per GB-month
  • Outbound bandwidth - $0.11 - $0.13 per GB
  • Inbound bandwidth - $0.09 - $0.11 per GB

Under these rates, developers might expect to pay around $40 per month, according to one estimate I came across.

Google also released more details about its new caching and image storage and manipulation APIs. The caching API will be based on the open source memcached project, a “high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load,” according to its Web site. In essence, the system figures out which pages are accessed most or drain the most resources and stores them in memory to reduce access time.

The Images API will handle uploading, storage and presentation to users of images such as photos and avatars. The Images API provides the same scalable infrastructure as used in Google’s Picasa Web Albums. “With this API, you can resize, crop, rotate and flip images in JPEG, PNG, GIF (including animated), BMP, TIFF, and ICO formats as well as adjust their contrast and color levels using an automated algorithm for correcting photographs,” according to the API’s Overview page. Other image transformations capabilities will include flip, crop, rotate, resize and thumbnails.