Communication

What Are Communication APIs?

Communication APIs are the delivery layer for every message your application sends to users — from the OTP code in a login flow to the appointment reminder text before a doctor visit, to the transactional email confirming an order. Getting these right is critical: delayed SMS kills conversion on 2FA flows; email deliverability failures mean lost revenue; missed push notifications mean churned users. Managed communication APIs handle carrier routing, anti-spam compliance, delivery receipts, and global reach so your team doesn't have to.

Common Implementation Patterns

• OTP and 2FA verification via SMS with automatic fallback to voice call
• Transactional email (receipts, password resets, invoices) with DKIM/SPF managed by the provider
• WhatsApp Business messaging for markets where WhatsApp dominates over SMS
• Push notifications (FCM/APNs) with topic subscriptions and rich-media payloads
• In-app chat with persistent history, typing indicators, and read receipts
• Programmatic phone calls for appointment reminders and fraud verification

Choosing Your Communication Stack

Twilio is the market standard for SMS and voice — reliable, global, with SDKs in 9 languages and the deepest documentation. SendGrid (now part of Twilio) handles transactional email at massive scale with a generous free tier of 100 emails/day. Resend is the modern developer favourite for email — clean API, excellent React Email template support, and generous free tier. Firebase Cloud Messaging handles push notifications for Android and iOS at no cost. Sendbird and Stream Chat provide production-ready in-app chat SDKs for mobile and web. Budget tip: for SMS, always compare Twilio, MessageBird, and Vonage — pricing varies by 30–50% depending on destination country.