1. Phone numbers validation

Date: 2025-07-21

Status

Accepted

Context

Users entered invalid phone numbers, which led to failed SMS deliveries.

Decision

We have implemented phone number validation for all numbers to which we send SMS messages. We do not validate phone numbers that are not used for sending SMS messages. This is because users may enter multiple numbers separated by commas, which could otherwise result in validation errors.

Consequences

We save approximately 40% of our SMS sending budget, which amounts to about $400 per year.