Ken Chen discusses the significance of performance evaluation and tuning in application development, highlighting how an unresponsive application can result from inadequate resource provisioning and poorly tuned software. To address this, he developed Keyhole, an open-source tool designed to quickly gather statistics from MongoDB clusters and provide performance analytics summaries. Keyhole offers comprehensive insights akin to a CAT scan for a MongoDB cluster, including configurations, statistics, schema, indexes, and resource usage, helping identify performance issues such as hardware limitations or inefficient queries. The tool is written in Go, and its capabilities include performing load tests to evaluate MongoDB performance isolated from applications, generating HTML reports, and assessing index redundancy and usage for optimization. It also allows users to validate new MongoDB installations and check the health of existing clusters, with detailed outputs available for further analysis. The blog post is the first part of a series, with the second part set to explore MongoDB application performance tuning through log and diagnostic data analysis.