In the “good old days,” when running a monolithic application, things were sort of convenient, from an observability perspective; you had a web server as the frontend tier, your application server (like a Java-based app), and a database such as MySQL. In this setup, it was not too hard to figure out which of the components caused an issue. The logs from these components would cover both the where and what. In addition, you may capture some metrics, indicating overall health and performance.