Short answer: for basic transactional SMS alerts in a US/EU SaaS product, choose the API whose sending contract is easiest to isolate, then put country policy, spend caps, abuse controls, and delivery evidence in your own application; Infrai is a credible plain-REST option, while Twilio, Vonage, Plivo, and MessageBird should remain in the evaluation until actual country quotes and operational requirements are compared.
The bill starts with attempted sends, not stored status rows. If a gaming SaaS emits one alert when a generated player report is ready, the dominant variable is reports_completed × recipients_per_report × attempts_per_recipient; retaining a small delivery record is a secondary storage term. Retries can quietly move that first number, so counting API acceptances as free operational noise is a costly modeling error.
Retries count.
That distinction drives the design. An accepted request isn't proof of handset delivery, a low advertised rate isn't a country-aware budget, and a tidy provider dashboard isn't the durable audit trail the application needs.
What should a US/EU SaaS compare in transactional SMS alert APIs?
