This document discusses different strategies for upgrading Kafka Streams applications: rolling upgrades, blue-green deployments, and full restarts. It describes the basic Kafka Streams architecture including topics, state stores, and sub-topologies. It then explains the benefits, considerations, and when to use each upgrade strategy. Rolling upgrades avoid downtime but require careful planning. Blue-green deployments minimize downtime through parallel workloads but are more expensive. Full restarts incur downtime but are needed when upgrading all legacy applications.