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.NET 9 Microservices, Modular Monolith: DDD & Vertical Slice (Udemy.com)

Build an MVP in .NET 9 with C# microservices, DDD, CQRS, Clean Architecture & Vertical Slice, gRPC, messaging & Docker

Created by: Laurentiu Dumitrescu

Last updated April 2026

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What you will learn

  • Build 5 real microservices end-to-end — and see how modular monoliths fit in the same solution
  • Implement CQRS & Interceptors using both MediatR and FastEndpoints
  • Use gRPC for synchronous and MassTransit for asynchronous microservices communication
  • Design your system first with C4 diagrams, sequence diagrams and tactical DDD
  • Apply Vertical Slice and Clean Architecture to organize your microservices
  • Apply DDD to model aggregates, value objects and domain events around real business rules
  • Use Docker to containerize your microservices & external dependencies
  • Build flexible Minimal APIs using ASP.NET Core, with or without Carter
  • Build global exception handling middleware for clean, consistent error responses
  • Apply interception with endpoint filters, MediatR behaviors, pre-processors and gRPC interceptors
  • Use GraphQL to query and filter efficiently from a PostgreSQL database

How it compares

Against the other 815 rated Udemy courses in Web Development on CourseDuck:

  • Rating4.6 out of 5higher than 70% of them
  • Reviews105#644 of 816 by number of reviews
  • Length25.7 hourslonger than 85% of them
  • Last updatedApril 2026more recently than 81% of them

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Course Description

In this course we build real C# microservices and a modular monolith in a .NET 9 solution from scratch: a full MVP for managing scientific articles. You’ll learn how to apply Domain-Driven Design (DDD) and Vertical Slice Architecture to real business workflows — not toy examples.

You'll see how to turn business requirements into bounded contexts, aggregates, value objects and domain events, then implement them end-to-end with C#, ASP.NET Core, EF Core, gRPC, messaging and Docker. Each feature is built as a vertical slice: from the API contract and validation, through command handlers and domain logic, down to persistence and tests.

We implement both synchronous and asynchronous communication between services. You'll learn to differentiate between Core/Critical services (using direct gRPC for reliability) and Domain services (using event-driven architecture with messaging). This gives you practical experience with CQRS and event-driven patterns in a real distributed system.

Along the way we focus on practical architecture decisions: when to use microservices vs a modular monolith, how to design rich domains instead of "anemic" models, how to apply CQRS with MediatR, and how to keep code clean, simple and testable while services communicate over gRPC and messaging.

By the end of this course you will be able to:

  • Design and implement .NET 9 microservices and a modular monolith with DDD and Clean Architecture

  • Apply Vertical Slice, CQRS and event-driven architecture in a real project

  • Model solid aggregates, value objects and domain events

  • Implement sync (gRPC) and async (messaging) communication between services

  • Structure solutions for long-term maintainability and clear boundaries

  • Make pragmatic architecture trade-offs, instead of just following theory

Who is this course for?

Intermediate to senior C# / .NET developers who have already built at least one Web API and want to learn how to design real systems with DDD and microservices/modular monolith.
Ambitious junior developers who are comfortable with C#, ASP.NET Core Web APIs and SQL, and want to move to the next level into architecture and system design.

Software architects who want a concrete end-to-end .NET 9 example of modern architecture patterns.

You should be comfortable with C# fundamentals, have some experience with ASP.NET Core Web APIs, and know basic SQL (tables, relationships, CRUD). It is recommended that this is not your very first C# project, nevertheless I will guide you step by step from an empty solution to a working, production-style architecture.

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Instructor Details

Laurentiu Dumitrescu

I’m a Software Architect with 15+ years of experience in building scalable .NET & Azure applications. I specialize in Microservices, Domain-Driven Design, and modern backend architecture.

My courses are built around real-life applications and hands-on experience. They don’t just teach theory—they help you make practical decisions in real projects and build the confidence you need to grow your career and get hired as an experienced developer.

I hold certifications including Microsoft Azure Architect Expert, TOGAF® Practitioner, and Scrum Product Owner (PSPO I), reflecting my commitment to both technical depth and strategic thinking.

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Reviews

4.6

105 ratings on Udemy

Select a bar to show only those reviews.Select the bar again to show every rating.

By Vladimir Jelovac on 6/15/2026

One of the best courses that I saw here. I would even say- the best so farContains a lot of practical things combined with theory and good explanations. Especially what I liked here are start of each module where author explains what we want to do, what is this meaning and purpose of all this and goes into very important things like explanations of workflows, user stories, requirements, different types of diagrams, integration scenarios and architecture as a whole. As somebody who is very long in this business I would say that I saw a great amount of experience here, which combined created this small masterpiece. There is only one downside here - this is definitely not for beginners or somebody who is coding only with help of AI. For this to follow you really need to understand the code, technical difficulties and have entire picture in head and for this you also need at least few years of real experience in business. Again, from my side, all respect goes to the author, we need more people like him.

By Luiza Dumitrescu on 1/15/2026

I used to be a software developer and now I work as a Product Owner. I enrolled in this course because I want to better understand modern best practices for building applications. The theory part is crystal clear and very useful. I’ve also watched about half of the first hands-on module: the business and architecture lectures are really insightful, and I had no problem following the coding parts. Highly recommend it!"

By Sethu Raman on 1/14/2026

I have been searching for a course that will cover everything in Microservices Auth, Grpc, Cache, RabbitMQ, MinimalAPI, CQRS, Validation, Docker, DDD and much more especially how to design each part in architect level is amazing. One small request to Laurentiu is if possible to include Gateways (Ocelot, YARP), Dapper, Polly, Circuit breaker, Health checks and Fault tolerance --> If possible even in separate course. Thought to finish this course in 3 months but man there is tons of things to learn and practice. Thank you very much Laurentiu for designing this course.

By Łukasz Biedrzycki on 1/6/2026

the theory part is really well explained. Clear, to the point, nice visuals also. the hands-ons are really heavy, in a good way, lots of things to learn. lot of techs also. Though, there are a few lectures which needs updates, few compilation/running issues.

By Alina Dragus on 1/1/2026

i’m a project manager working in finance, and I’ve also been involved in several software projects as a consultant. A friend recommended this course to me, suggesting I focus on the business-oriented lectures, and I’m glad I did. I found the course genuinely enlighting. It was very interesting to see how an architect approaches domain modeling and how a product owner translates business needs into features and user stories. Now I understand better the reasoning behind many technical and product decisions I encounter in my projects. I only watched the business-focused and some architectural lectures, so I can’t coment on the code itself, but from a product perspective, the course was very valuable.

By Cristi Dumitru on 12/13/2025

As a .NET/Azure architect, I took this to see how others design modern apps. The architecture (DDD, vertical slices, CQRS, gRPC) is pragmatic and production-ready. Starts slow for my level, but the later workflows get nicely complex and relevant. And also the github content is very rich, kind of a project you want to have to get inspired from.

By Amith V on 12/10/2025

Not very beginner-friendly, but extremely valuable for mid-level .NET developers. This course really helps improve architectural thinking and gives a clear understanding of how to approach real-world problems. It explains modern architecture patterns in a practical way, making it a great learning experience. Thanks to the instructor for putting together such a helpful and insightful course.

By Chirita Ovidiu on 12/8/2025

I was pleasantly surprised by this course. I initially started it out of curiosity for a few specific chapters, but it was compelling enough to keep me watching until the very end. Unlike other approaches, this course focuses on a real-world business case and offers a solution to a practical problem. If you are a start-up looking to build software, this course generously covers every aspect of development in a highly professional manner. You can clearly see the author's extensive experience with both mainstream tools and advanced concepts. Essentially, you can follow the course, download the code, and adapt it to your own use case. I would like to thank the author for all the hard work put into this.

By Ria Dms on 12/6/2025

I’m a CS student first time touching C# and .NET. This course is definitely above my level, but in a good way. I didn’t always understand the code, but I loved seeing how a “serious” app is structured with microservices and DDD. It’s not a beginner C# tutorial – it’s more like a peek into how senior devs think. I’m keeping it in my library and will rewatch it after I finish a basic C# course.

By Herry Wijaya on 12/1/2025

-not beginner friendly -missing code , error reason is because the code that is shown in the current watched video will be different from the next. That's why his IDE doesn't show error on typed syntax on the current one

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Overall Score : 92 / 100