Your system sends the message itself: order updates, alerts and reminders on the channels customers already use.
Your system should tell people what happened without someone typing a message. I connect it to WhatsApp, SMS and push notifications, and to other services over their APIs.
An order is placed or its status changes, and the system sends the WhatsApp or SMS message itself.
Push notifications for web and mobile apps through OneSignal.
Connections to the outside services your business depends on, over their APIs.
Messages go out through queues, so a slow provider does not hold up the person using your app.
A B2B sales business needed procurement, inventory, sales, customer accounts and orders in one system, on web and mobile.
REST APIs for the web and mobile apps, a multi-database architecture, the main ledger and financial reporting, and WhatsApp, SMS and push notifications.
I reply to every message, usually within a day.