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To maintain performance and availability across a diverse base of client apps, it's critical to maintain app traffic within the limits of the capacity of your APIs and backend services. It's also important to ensure that apps don't consume more resources than permitted.
Apigee Edge provides two mechanisms that enable you to optimize traffic management to minimize latency for apps while maintaining the health of backend services. Each policy type addresses a distinct aspect of traffic management. In some cases, you might use both policy types in a single API proxy.
Watch this video for an introduction to API traffic management policies.
SpikeArrest
This policy smooths traffic spikes by dividing a limit that you define into smaller intervals. For example, if you define a limit of 100 messages per second, the SpikeArrest policy enforces a limit of about 1 request every 10 milliseconds (1000 / 100); and 30 messages per minute is smoothed into about 1 request every 2 seconds (60 / 30). The SpikeArrest limit should be close to capacity calculated for either your backend service or the API proxy itself. The limit should also be configured for shorter time intervals, such as seconds or minutes. This policy should be used to prevent sudden traffic bursts caused by malicious attackers attempting to disrupt a service using a denial-of-service (DOS) attack or by buggy client applications.
See SpikeArrest policy.
Quota
This policy enforces consumption limits on client apps by maintaining a distributed 'counter' that tallies incoming requests. The counter can tally API calls for any identifiable entity, including apps, developers, API keys, access tokens, and so on. Usually, API keys are used to identify client apps. This policy is computationally expensive, so for high-traffic APIs, it should be configured for longer time intervals, such as a day or month. This policy should be used to enforce business contracts or SLAs with developers and partners, rather than for operational traffic management.
See Quota policy.