The document discusses how MetricsHub optimized its public cloud architecture using Cassandra to store massive amounts of telemetry data in a highly scalable and cost-effective way. It describes how MetricsHub grew to monitor over 8000 VMs and collect 200 million data points per hour. It explains how Cassandra provided a more scalable and reliable solution than Redis or SQL for MetricsHub's use case of aggregating and analyzing streaming telemetry data in real-time. The architecture diagram shows how MetricsHub uses a combination of Azure PaaS and IaaS resources, including a 32 node Cassandra cluster, to monitor customer resources.