The runtime environment monitors the system resources used by the application and limits how much the app can consume. For the resources you pay for, such as CPU time and storage, you set these limits yourself by allocating a budget in the Administration Console. App Engine also enforces several system-wide limits that protect the integrity of the servers and their ability to serve multiple apps.
In App Engine parlance, “quotas” are resource limits that refresh at the beginning of each calendar day (at midnight, Pacific Time). You can monitor your application’s daily consumption of quotas using the Administration Console, in the Quota Details section.
Since Google may change how the limits are set as the system is tuned for performance, we won’t state some of the specific values of these limits in this book. You can find the actual values of these limits in the official App Engine documentation. Google has said it will give 90 days’ notice before changing limits in a way that would affect existing apps.
Several system-wide limits specify how requests can behave. These include the size and number of requests over a period of time, and the bandwidth consumed by inbound and outbound network traffic.
One important request limit is the request timer. An application has 30 seconds to respond to a request.
Near the end of the 30 seconds, the server raises an exception that the application can catch for the purposes of exiting cleanly or returning a user-friendly ...