Apache Pulsar is a fast, durable, and flexible pub/sub messaging system designed for high throughput and multi-tenancy, supporting up to 1.8 million messages per second with geo-replication capabilities. It overcomes limitations of existing solutions like Kafka by providing a unified messaging model, low latency, and efficient management of large backlogs. Pulsar's architecture separates brokers and storage, allowing for scalable and low-latency message processing suitable for various applications, including notifications and event-driven microservices.