This document discusses Cassandra metrics and provides some key metrics to monitor for Cassandra. It notes that while Cassandra is fault tolerant, issues can arise if the number of events is not monitored. It then lists some key stages and metrics to watch, including the ReadStage, RequestResponseStage, MutationStage, and provides an example of using nodetool tpstats and JMX to access metrics on tasks processed and pending in different stages. The document also notes that while there are many metrics, without context they are not very useful, and it is missing some important metrics like heap and OS metrics.