In my case, it's not wanting to avoid external dependencies - it's how hard those dependencies are. An external that you can swap out in an afternoon is a perf

In my case, it's not wanting to avoid external dependencies - it's how hard those dependencies are. An external that you can swap out in an afternoon is a perfectly healthy vendor relationship. But if, eg, some machination flagged your account out of the blue, and your only recourse is to stare blankly at the screen in disbelief, this is not a healthy dependency. So as long as other sms gateways/delivery services are available, his dependency isn't "Twilio", it's "an sms gateway/delivery service".