This document provides guidance on diagnosing problems in Cassandra production systems. It outlines various preventative monitoring measures that can be used to monitor systems such as OpsCenter, Munin, Nagios, and Graphite. When problems occur, it recommends narrowing down the issue by examining areas like consistency, repair, queries, compaction, and system metrics. Specific tools are presented for analyzing compaction, system utilities, histograms, query tracing, Java garbage collection, and profiling garbage collection issues.