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Proxy Limits

Twilio Proxy has a number of limits in place which will constrain certain elements of the system and how it is used.

The Proxy limits are enforced at the Service instance level (except for Service list limits which are enforced at the Account level). These limits are set within a Service instance scope.

Number Pool Limits

Each service can have a maximum of 5000 Reserved numbers and 500 dynamic/non-reserved numbers.

Active Participants per Number

We recommend, but do not enforce, a limit of 100 participants associated with a given number in active sessions at any given time. See for more information on proxy number management.

Throughput Limits

Limits of this type will impact the number of simultaneous actions that can be performed within a Service Instance.

Requests Per Second

RPS is the guaranteed Requests Per Second against a given endpoint that a Service instance will support. All Service instances have a baseline of 30 RPS per endpoint. Proxy will allow short bursts above the baseline RPS - up to 5x the baseline. If the bursts become sustained throughput, the Service will start rejecting requests.

Please note that the RPS limit is currently enforced for Read actions against Services, Sessions, Participants and Interactions.

How This Works

The request limit is based on average request rate in 5s sliding window. For example, for 30 req/s limit we allow burst up to 150 req/s. After this your application client request logic needs to wait until average goes below threshold to make any query requests again against that endpoint.

Requests that go over RPS threshold are rejected with HTTP status code 429 Too Many Requests.

When the Throughput is Exceeded

For reliable handling of short-term bursts of requests towards the Proxy REST API, please make sure your backend application implements a retry logic. When your application receives HTTP status code 429 back from the Proxy service, it should repeat the request several times, using a good exponential back-off algorithm like the one advocated by Amazon.

Data Length/Size Limits

Limits for user provided data in UTF-8 characters. If a payload limit is specified in bytes, we assume that the data is serialized using UTF-8 encoding where each character (e.g. emoticon) may take more than one byte.

Resource Property Limits

Resource Field Maximum length / Size
Service UniqueName 191 characters
Service CallbackUrl 4000 characters
Service InterceptCallbackUrl 4000 characters
Service OutOfSessionCallbackUrl 4000 characters
Session UniqueName 191 characters
Session Ttl 0 < ttl < 2147483647
Participant FriendlyName 255 characters
Participant Identifier 191 characters
Participant ProxyIdentifier 255 characters
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