SMS

Reach someone who is not looking at a screen.

Text a number through your own Twilio connection. A chat message is easy to miss and an email is easy to sleep through. SMS is the point where an alert stops being informational and starts being a page.

Your own Twilio account. You control the sending number and pay Twilio directly, rather than through a marked-up bundle.
Works without data. SMS arrives over the cellular network, so it reaches a phone with no wifi and no mobile data.
Encrypted at rest. Your Twilio credentials are encrypted at rest.

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01 · Using it well

Reserve it for what warrants it.

SMS costs money per message and interrupts a person directly. Both are reasons to put it deliberately rather than everywhere.

Put it behind a Wait

Post to a channel immediately and only text after the outage has run for a few minutes. Most brief failures resolve before the text is ever sent.

Second tier, not first

Use a chat channel for awareness and SMS for the outages nobody has picked up. That keeps the interruption meaningful.

Pair with acknowledgement

Email the on-call engineer with an Acknowledge button, then text a second person only if nobody claims it.

Critical services only

Because flows belong to individual monitors, a payment API can text while a background job stays in a channel.

Mind the cooldown

Each notify step has a flap cooldown, fifteen minutes by default, which also limits how much a flapping monitor can cost you.

Fire once per incident

The default, and the right setting for SMS. Firing on every check would text on every failed probe.

Questions

Common questions

Do I need my own Twilio account to send SMS?

Yes. SMS is sent through your own Twilio connection, which means you control the sending number and pay Twilio directly for the messages rather than through a marked-up bundle.

How do I stop SMS costs running away during a flapping outage?

Several controls stack. Notify steps fire once per incident by default, each step has a flap cooldown of fifteen minutes, and the monitor confirm down after setting means brief failures never create an incident at all. Putting the SMS step behind a Wait block is the other common approach.

Should SMS be my first alert?

Usually not. Most teams post to a chat channel first and reserve SMS for outages that are still running after a few minutes, which keeps the interruption meaningful and the cost down.

What is the difference between SMS and a phone call?

A text arrives silently unless the recipient has notifications configured to be loud. A phone call rings through in situations where a text would not, so it is the escalation above SMS rather than an alternative to it.