The _cat API is a valuable tool for command-line debugging and monitoring in Elasticsearch, providing a more streamlined alternative to the JSON-oriented main API. It allows users to efficiently gather information on node memory usage, thread pool activity, and index metrics, which are crucial for identifying and addressing performance issues. By utilizing command-line utilities like curl, sort, and watch, users can quickly pinpoint nodes experiencing high memory pressure, monitor thread pool operations, and track data migration between clusters. These capabilities make the _cat API particularly useful for managing Elasticsearch clusters in real-time, offering immediate insights into system performance and potential bottlenecks. Additionally, the article highlights the versatility of combining the _cat API with other command-line tools to create custom monitoring solutions, emphasizing its role in simplifying Elasticsearch administration and troubleshooting.