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Rate Limits

Default Voice Rate Limits

Call throughput is limited at the Space level, at a rate of 1 CPS (Call Per Second).

Customers can also request additional increases to their Space limits.

Higher CPS is available. For more information, contact Sales or Support.

Default SMS Rate Limits

Toll Free Numbers3 messages per second
Long Code (10 Digit Local Numbers)1 message per second
Short Code10 messages per second
Message Segments

Rate limits refer to messages per second or MPS, but it is important to remember that 1 message = 1 segment. For example, the rate limit for Toll Free Numbers, 3 messages per second, is 3 segments per second.
Check out our article about Messaging Character Limits for more information about what makes up a message segment!

Queue and Backlog System

The backlog defines how many pending instances of a resource an account can have in the system before SignalWire stops accepting more. Without a backlog to stop them, a fraudulent user could load up millions of outbound calls and just let the system run them to spam users. Limiting the backlog still allows for high throughput and stops spammers from easily abusing the system.

For example, if you are sending calls and messages from long code numbers, they will send out at 1 message/call per second. If you queue up 10 calls/messages per second per number, SignalWire will still queue the excess and send them out at 1 per second. If you have the default call/message backlog of 10,000, you can send your messages to SignalWire at any rate you want as long as your queue stays under 10,000, and we will continue to send sequentially at 1 per second. However, if your queue hits the backlog of 10,000, SignalWire will reject all messages/calls after that point until the queue decreases. This essentially amounts to 10,000 messages/calls per hour at 1MPS.

If you would like to raise your call or message backlog, you can do so by requesting an increase to your Space limits.

High Throughput Phone Numbers

If you need a higher throughput than the defaults for calling/voice shown above, we do have solutions available! Reach out to or check out our article about high throughput messaging.

Overall API Limits

Overall API requests are limited to 13800 requests over 10 seconds for POST/PUT/PATCH requests. GET and DELETE requests are effectively unlimited.

This limit applies to all API requests across the SignalWire system. Every HTTP request made by a user can see their current limit and how many they have left in their X-Header.