This document discusses monitoring big data systems in a simple way. It begins with introducing the speaker and their background. The rest of the document outlines monitoring concepts, common big data architectures involving Spark and Cassandra, and potential problems that can arise. It then provides recommendations for setting up a monitoring stack involving metrics collection, logging, dashboards, and alerting. Specifically, it recommends using Graphite, Grafana, Coralogix, and Redash. The document emphasizes the importance of correlating application and system metrics and asking the right monitoring questions.