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[Parameter] quotaUser [Meaning] Alternative to userIp. [Notes] 
Lets you enforce per-user quotas from a server-side application even in cases when the user's IP address is unknown. This can occur, for example, with applications that run cron jobs on App Engine on a user's behalf. You can choose any arbitrary string that uniquely identifies a user, but it is limited to 40 characters. Overrides userIp if both are provided. Learn more about capping usage.
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