App Engine Services Summary
Datastore: The Datastore is a schemaless object datastore, with a query engine and atomic transactions.
Blobstore API: The Blobstore API allows your app to serve data objects, called blobs, that are much larger than the size allowed for objects in the Datastore service.
Capabilities API: With the Capabilities API, your application can detect outages and scheduled downtime for specific API capabilities.
Images API: The Images API can resize, rotate, flip, and crop images. It can also enhance photographs using a predefined algorithm.
Mail API: The Mail API sends email messages on behalf of the app's administrators, and on behalf of users with Google Accounts. Apps can receive email at various addresses.
Memcache: Memcache is a distributed in-memory data cache to be used in front of or in place of robust persistent storage for some tasks.
Namespace: The Namespaces feature allows you to implement multitenancy in your applications.
OAuth: OAuth is a protocol that allows a user to grant a third party limited permission to access a web application on her behalf, without sharing her credentials (username and password) with the third party.
Prospective Search (experimental): Prospective search allows an application to register a large set of queries that are simultaneously matched against a stream of input documents.
Task Queue API: The Task Queue API allows applications to perform work initiated by a user request, outside of that request.
URL Fetch API: The URL Fetch API allows applications to fetch resources and communicate with other hosts over the Internet using HTTP and HTTPS requests.
Users API: The Users API allows applications to authenticate users who have Google Accounts, accounts on your own Google Apps domain, or OpenID identifiers. (Note that the support for OpenID is experimental.)
XMPP API: The XMPP API allows applications to send and receive instant messages to and from users of XMPP-compatible instant message services, including Google Talk.