Using Twilio SMS API, can I specify multiple destination phones in one post?

Question

Twilio limits long code SMS to 1/sec. To improve my throughput, I split my batch into 5 phone numbers. I've found each HTTP POST to the Twilio API takes about 0.5 seconds.

One would think using 5 twilio phone numbers to send a message to 1000 cell phones would take 200 seconds, but it will take 500 seconds just to POST the requests. So two phone numbers will double my throughput, but more would not make a difference.

Am I missing something? I was thinking it would be nice if the API would take a list of phone numbers for the "To" parameter. I don't want to pay for a short code, but even if I do it seems the maximum throughput is 2/sec unless you resort to the complexity of having multiple threads feeding Twilio.

I've noticed TwiML during a call let's you include multiple sms nodes when constructing a response so it seems like there should be a way to do the same for outbound SMS.

Answer 1

Twilio Evangelist here. At the moment, we require that you submit each outgoing SMS message as its own API request.

The current rate limit on a longcode is 1 message per second. If more messages per second are sent, Twilio queues them up and sends them out at a rate of 1 per second.

A potential workaround is to make async requests across multiple phone numbers. This can be accomplished with the twilio node.js module or an evented framework such as EventMachine for Ruby or a similar toolset for your language of choice.

Hope this helps!

Answer 2

Here's a more modern answer. Twilio now supports Messaging Services. It basically lets you create a service that can group multiple outbound phone numbers together. So, when you fire off requests for a text to be sent, it can use ALL the numbers in the message group to perform the sending. This effectively overcomes the 1 text per second limit.

Messaging services also comes with Copilot. It adds several features such as "sticky sender". This ensures the same end user always gets texts from the same number in the pool instead of getting a text from different numbers.

Answer 3

If you are using the trial account, even looping with a 5s timeout between each item in the array did not work for me. And that was for just two numbers. Once I upgraded the account the code worked immediately without needing a timeout.

You know it's the trial account if the SMS you receive (when sending to only one number) says "Sent from your Twilio trial account - ".