In the ever-evolving landscape of software development, one architectural paradigm has risen to the forefront, promising unprecedented flexibility, scalability, and integration capabilities: microservices. The transition from monolithic mainframe applications to microservices has become a pivotal milestone for organizations seeking to thrive in the digital age. "Microservices: Decomposing Monolithic Mainframe Applications" is a book that delves into the heart of this transformative journey. It's a guide for those who dare to break free from the constraints of outdated, monolithic systems and embrace the future of software architecture. In the following pages, we will embark on a voyage through the intricacies of microservices, discovering how they empower organizations to develop, scale, and integrate their applications like never before. We'll explore the principles that underpin the microservices architecture and the symbiotic relationship it shares with containerization technologies. Decomposing a monolithic mainframe application is no small feat. It requires a strategic approach and careful consideration. This book will help you assess your monolith, identify microservices boundaries, and adopt effective strategies for a seamless transition. Containerization plays a pivotal role in the microservices ecosystem, enabling deployment, scaling, and management with ease. We'll dive into containerization technologies such as Docker and Kubernetes, unveiling their benefits and how they mesh seamlessly with the microservices architecture. Effective communication and API design are the lifeblood of microservices. We'll explore best practices for designing APIs, choosing communication protocols, and managing service discovery. You'll learn how to optimize data exchange and serialization for a robust microservices ecosystem. Scalability and resilience are key aspects of microservices. We'll cover horizontal and vertical scaling, load balancing, and fault tolerance strategies, ensuring that your microservices can handle both routine traffic and unexpected challenges. DevOps and continuous integration/continuous deployment (CI/CD) practices are essential for managing the dynamic nature of microservices. This book will shed light on DevOps culture, infrastructure as code, and testing and monitoring strategies that can help you maintain a healthy microservices environment. Security and compliance are paramount in the world of microservices, especially in the face of increased data breaches and regulations. You'll gain insights into securing your microservices, handling authentication, authorization, and data protection, all while ensuring compliance with relevant standards.