This book is a comprehensive roadmap for transitioning legacy systems into agile, cloud-native, and intelligent architectures. Whether you’re a software architect, DevOps engineer, or technology decision-maker, this book is your essential guide to navigating the evolving landscape of modern application development. The book starts with an overview of why modernisation is imperative in today’s fast-paced environment, highlighting the limitations of legacy architectures and the advantages of embracing cloud-native models. From building a solid modernisation roadmap to understanding the anatomy of legacy systems like monoliths and N-tier applications, readers will gain practical insights into planning and execution. As the book progresses, it delves into the core of modern software architecture—microservices, containers, Kubernetes, and API-first design—explaining how to design, deploy, and scale distributed systems. Real-world implementations using Spring Boot, Node.js, React, and cloud platforms provide hands-on guidance for developers. Further, chapters cover performance optimisation, observability with Prometheus and Grafana, centralised logging, and CI/CD pipeline automation with Jenkins and GitHub Actions. Security is woven throughout, with detailed chapters on OAuth, API gateway protection, DevSecOps, and regulatory compliance, including GDPR and HIPAA. The book culminates with cutting-edge applications of AI and ML—chatbots, predictive analytics, and intelligent automation—showing how AI can enhance both customer experience and backend operations. The book is a collection of multiple patterns, best practices, and real-world use cases, which equip the reader to lead successful modernisation initiatives that are secure, scalable, and future-ready. What you will learn: What are the limitations of legacy architectures and the advantages of embracing cloud-native models. Understand the principles and strategies behind modernising legacy applications for...