Full-stack observability is a crucial concept in modern software development that focuses on embedding data observability into every layer of a software stack, providing insights into complex, distributed systems. As architecture trends shift towards distributed and containerized environments, the need for observability grows, allowing teams to monitor, analyze, and troubleshoot issues across various system components effectively. Unlike traditional monitoring, which relies on predefined metrics, observability enables dynamic querying of emitted data to understand a system's behavior. Full-stack observability integrates four key telemetry types—metrics, logs, traces, and security data—each contributing unique insights into system health and performance. Metrics track system health over time, logs provide detailed event records, traces offer context for requests across microservices, and security data helps identify potential threats. An observability platform aggregates these telemetry types, offering a comprehensive view of system behavior, which enhances cross-team collaboration, accelerates issue resolution, and supports the safe adoption of new technologies while maintaining system performance and security.