Monolith to Microservices - The Modernization Playbook

Legacy monoliths are everywhere. Rewriting them from scratch is risky, expensive, and often unnecessary.

In Monolith to Microservices - The Modernization Playbook, you will learn how to modernize a real-world legacy application step by step using practical software architecture patterns used in enterprise systems.

This is not a theory-only microservices course. You will work through a complete modernization journey: starting with a monolith, discovering domain boundaries, moving toward a modular monolith, introducing domain events, adding a Strangler Fig API Gateway, extracting a real microservice, adding a service-owned database, implementing the Outbox Pattern, integrating RabbitMQ, and finally adding observability and resilience with OpenTelemetry, Aspire Dashboard, and Elastic/ELK.

You will learn how to break a monolith safely without breaking the business.

The course uses a healthcare claims processing system as the case study, making the architecture realistic enough to demonstrate real modernization decisions: claims, members, policies, providers, documents, payments, notifications, audit trails, and reporting.

By the end, you will understand not only how microservices are built, but how they are extracted from existing systems in a controlled, domain-driven, production-minded way.

What You’ll Learn

• Modernize a legacy monolith without a risky big-bang rewrite

• Apply Domain-Driven Design to discover real service boundaries

• Refactor a monolith into a modular monolith with clear module ownership

• Use domain events to decouple business capabilities

• Implement the Strangler Fig Pattern with an API Gateway

• Extract a Documents microservice from an existing system

• Add a service-owned database to remove shared database dependency

• Implement the Outbox Pattern for reliable cross-service events

• Replace local integration events with RabbitMQ

• Add OpenTelemetry tracing, metrics, and logs

• Use Aspire Dashboard for local observability

• Understand how Elastic/ELK fits as a production-style observability option

• Add basic gateway resilience, correlation IDs, and operational visibility

• Build a modernization roadmap that is practical, incremental, and demo-ready

Who This Course Is For

• .NET developers working with legacy systems

• Backend engineers moving from monoliths to microservices

• Software architects designing modernization roadmaps

• Senior developers preparing for architecture responsibilities

• Teams that want practical DDD, modular monolith, and microservices guidance

• Developers tired of toy microservices examples and looking for a realistic migration path

Requirements

• Basic C# and ASP.NET Core knowledge

• Familiarity with REST APIs

• Basic Docker knowledge is helpful

• Some experience with enterprise applications or layered architecture is useful

• No prior microservices migration experience required