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Comment by matthewer | Hacker News Reader

Keep in mind that you can only send one message every second. That is a pretty low throttle. If your service were to take off you would probably need to switch to a bigger aggregator.

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To be clear, the throttle is 1 message per minute per phone number (which is $1/month), not per account.

-danielle (@twilio)

Really? One per minute per number? That's a pretty big limitation.

Edit: I think Danielle just mistyped. From the FAQ: "Each of your Twilio SMS-enabled phone numbers can send SMS messages at a rate of 1 message per second. You can make requests to Twilio as fast as you like, and Twilio will queue the messages, releasing them at a rate of 1 message per second. It is not possible to adjust this rate."

Eek yes, 1 msg per second per number... I think it's time for me to go to bed.

danielle (@twilio)

Either way, imagine you need to send out 100 messages. That would be 100 seconds (or even worse 100 minutes.) Imagine if you needed to send out 1,000 or a million. Its going to be hard to build a solely SMS service around this based on that limitation. I think this is awesome if you want to add SMS alerts to your existing website or build a proof of concept, but I don't think your going to build an SMS app on top of this API.

Well if your service is sending out 100 messages in one second then you can probably afford the $1-$2/month charge to add more numbers.

Especially since you are already paying $3 per minute for the 100 messages.

http://www.twilio.com/pricing-signup says that it's 3 cents/SMS - which, yes, works out to be $3 - but not because it's per minute.

My point is that you have 86,400 seconds in a day. Well before you are spending $864 per day maxing out the number of messages you can send, you have $1 in the bank to get another number.

But then again, having a bank of 100 phone numbers just to send the million messages you want to send within an hour sounds slightly annoying from a logistics perspective.

The point is: you buy more phone numbers at $1/month to increase your capacity.

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