Learn how Netflix manages and transmits contextual metadata across their complex microservices ecosystem in this 30-minute conference talk from KubeCon + CloudNativeCon. Discover strategies for handling ancillary request data including session information, routing strategies, and failure testing across services that span both gRPC and REST APIs in multiple programming languages. Explore the definition and importance of contextual metadata, understand how Netflix utilizes Protocol Buffers to define strict relationships in their polyglot environment, and examine techniques for propagating data across different inter-process communication transport frameworks with particular focus on gRPC metadata headers. Gain insights into lessons learned from scaling, managing, and observing these systems in production at Netflix's scale.