Kandasamy Selvaraj is a Principal Architect and performance engineering leader with over two decades of experience making high-volume distributed systems fast, reliable, and observable. For more than a decade of that journey, he has led performance engineering and observability initiatives for large-scale enterprise platforms and systems protecting workloads that process millions of transactions, and today applies that leadership to GenAI and agentic AI systems at enterprise-grade scale. This book is his view and his experience, independently researched, and not the views of any employer.