In today's cloud-centric landscape, achieving optimal systems performance is paramount. This presentation delves deep into the intricacies of monitoring complex systems. We'll begin by exploring the challenges and strategies associated with optimizing system performance, drawing upon foundational principles from renowned references in the field. Transitioning to the practical side, we'll delve into the real-world experiences of a leading cloud vendor in monitoring. By sharing insights from hands-on implementations and how our customers have effectively tailored monitoring solutions, attendees will gain a comprehensive understanding of best practices and pitfalls to avoid.