You can monitor MongoDB performance with the MMAPv1 storage engine by tracking throughput metrics, database performance, and resource utilization. Key areas to focus on include read and write operations, replication and oplog metrics, journaling, concurrent operations management, and errors. Monitoring these metrics can help you identify potential issues before they become user-facing problems, allowing you to optimize MongoDB's performance and ensure high availability. By using a combination of tools such as MongoDB's utilities, commands, or dedicated monitoring tools, you can collect and analyze metrics to gain visibility into your database's health, performance, resource usage, and potential areas for tuning.