There are limits to how quickly messages can be sent to wireless carrier networks. This guide explains how Twilio processes your message requests, and limitations for each phone number type.
Notice: You can send messages to Twilio at a rapid rate, as long as the requests do not max out Twilio's REST API concurrency limit. When this concurrency limit is reached, Twilio will begin responding to your requests with
HTTP 429, or Error code 20429. For more information, see Twilio API response Error 429 "Too Many Requests".
API request queuing
When Twilio receives message requests from your application, these requests are queued for delivery in the order we receive them. Each of your Twilio phone numbers has a separate queue, and each queue can hold up to 4 hours' worth of message segments based on the sending rate for a phone number type. For example, a local phone number from the US or Canada has a full queue of 14,400 message segments.
Twilio message request processing
The rate at which Twilio dequeues messages varies depending on the origination and destination in the message requests. Below is a quick summary of the default dequeue rate:
|Origination||Termination||Message Segments per Second (MPS)||Maximum Queue Length (Message Segments)|
|Twilio SMS-capable local, mobile or Hosted SMS number||US and Canada||1||14,400|
|Twilio US & CA Toll Free number (excluding Hosted SMS)||US and Canada||3||43,200|
|Any Twilio SMS-capable number or Alphanumeric sender ID||Other international countries||10||144,000|
|Twilio Short Code||US, Canada or UK||100*||1,440,000*|
*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 Services with 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.
Inbound messages are queued at 500 messages per second for each Twilio destination. Twilio will make an HTTP request to the request URL for each message received at your number. Therefore, please make sure your server is capable of handling the load if you are expecting a large amount of concurrent inbound traffic.
If you have further questions regarding message queue lengths and latency, please Contact Twilio Support.