Observability in software engineering, a practice essential for monitoring and understanding system performance, has evolved significantly over the years, especially with the transition from static three-tier applications to complex, cloud-native environments. Historically, Application Performance Monitoring (APM) tools focused on relatively stable infrastructures, but the modern landscape demands a more dynamic approach due to continuous changes in virtual infrastructure and services. For banking and financial institutions, adopting modern observability practices is crucial to maintaining robust and secure systems in the face of rapid feature releases and increasing complexity. This shift involves integrating observability as a core component of software development, often referred to as "Shift-Left," where developers proactively define necessary observability levels during the coding process. By leveraging tools like OpenTelemetry and adopting progressive delivery techniques such as feature flagging, organizations can ensure that observability is part of every stage in the software delivery pipeline. This approach not only helps in identifying and mitigating potential security threats but also enhances overall system reliability, enabling banks to deliver innovative and competitive digital experiences.