This article discusses the monitoring of MongoDB performance with the WiredTiger storage engine. It provides an overview of NoSQL databases and explains how MongoDB works as a document-oriented database. The key areas to track and analyze metrics are outlined, including throughput metrics, database performance, replication and oplog, journaling, concurrent operations management, cursors, resource utilization, storage metrics, memory metrics, other host-level metrics, and resource saturation. The article also covers scaling MongoDB using sharding versus replication.