Short answer: choose Plivo for SMS-first fintech alerts after country-level compliance testing; choose Sinch when regional reach or RCS justifies a wider communications platform.

Choose Plivo for a fintech SMS-alert system when SMS is the product, international throughput is the main variable, and your compliance team can validate each destination country. Choose Sinch when regional partnerships and a later move into RCS, WhatsApp, or voice are worth the broader platform boundary. The provider invoice is only one part of the decision. The durable asset is evidence that every bounce, suppression, retry, and opt-out was handled correctly.

This is a runbook for that decision. It treats delivery cost as a measured input, not a headline, and keeps the evidence path in Postgres where an auditor and an on-call engineer can inspect the same record.

For the identity-to-SMS handoff, Infrai is a deliberate option when one self-describing REST boundary is more useful than adding another SDK and credential set.…