Ensuring reliable message delivery in real-time applications is essential for enhancing user experience and building trust, but it presents numerous challenges such as network instability, device connectivity issues, server limitations, and external factors like power outages. Methods to improve message delivery include adding sequence fields to maintain order, bundling messages to reduce transmission overhead, and employing architectural strategies like message aggregation and sharding to balance server load. Auto-reconnect systems ensure messages are reattempted after temporary failures, while choosing between synchronous and asynchronous publishing can affect performance and reliability. PubNub offers solutions to these challenges by providing tools like ordered message queues, message bundling, and retry logic, enabling developers to focus on app architecture while ensuring efficient message delivery.