You can send messages to Twilio at a rapid rate as long as the requests do not reach Twilio's API concurrency limit which is at 100. There are, however, limits to how quickly messages can be sent into the carrier networks. To keep you in compliance, Twilio automatically queues your messages, delivering them to the carriers at the appropriate rates. To ensure your application is behaving as expected, it’s important for you to understand what is going on under the hood.
When Twilio receives message requests from your application, these requests are queued for delivery in the order we receive them. Each of your Twilio numbers has a separate queue. Each queue can hold up to 4 hours' worth of message segments based on the number's sending rate, e.g. a full queue is 14,400 segments for a US/Canada local number.
The rate at which Twilio dequeues messages from a given queue varies depending on the origination and destination in the message requests. Below is a quick summary of the default dequeue rate:
|Origination||Termination||Message Segment per Second (MPS)|
|Twilio SMS-capable local or mobile number||US and Canada||1|
|Twilio US & CA Toll Free number||US and Canada||3|
|Any Twilio SMS-capable number or Alphanumeric sender ID||Other international countries||10|
|Twilio Short Code||US, Canada or UK||100*|
*Contact Sales for more.
For example, consider the first row above when you are sending messages from a Twilio number from your project to a list of US recipients. We will process your requests and send them to the carrier networks for delivery at the rate of 1 message segment per second per Twilio phone number. This means that if you send Twilio 90 messages at the same time from the same Twilio number, it will take roughly 90 seconds for the last message to be delivered. Therefore, for time-sensitive messages, we recommend that you keep a close eye on the queue length and use additional Twilio numbers for sending when needed. Twilio highly recommends using Messaging Copilot to help manage multiple phone numbers.
Notice: the dequeue rate mentioned above is a rough estimate, and not an SLA for delivery speed. Multiple factors, such as traffic congestion or carrier issues may impact the actual delivery rate.
If you have further questions regarding message queue lengths and latency, please Contact Twilio Support.