Simple Notification Service (SNS)

Notifications lets you know when something happens with your resources in Oracle Cloud Infrastructure. Using alarms, event rules, and connectors, you can get human-readable messages through supported endpoints, including email and text messages (SMS). You can also automate tasks through custom HTTPS endpoints and Oracle Cloud Infrastructure Functions.

Firebase Cloud Messaging (FCM) is a cross-platform messaging solution that lets you reliably send messages at no cost.

This article provides a high-level overview of Azure Service Bus, a fully managed enterprise integration serverless message broker.

Amazon SNS is a managed messaging service for communication, allowing messaging between decoupled microservices applications or directly to users with SMS texts, mobile push, and email.