What are Projections in an Event Sourced Microservice Architecture?

In this video I will show you the different types of projections in an event-based microservice architecture and how you can use them.

Projections can be created in code in your microservice or in read-models when domain events are received and processed, for example, you process a published domain event and then store the result of the analysis in Oracle, MySQL, SQL Server, etc.

Serverless Microservices Online Courses

Update 04/03/2019: I have completed the FREE course: “Why you need serverless microservices, yesterday!“. Enroll for FREE!
At the moment, I’m working on four online courses in the following order:


Why You Need Serverless Microservices, Yesterday, FREE Course


In this course I will walk you through the many benefits of creating serverless microservices instead of the traditional node / instance approach including the use of containers. There are more than enough things to worry about when you want to create a new cloud system or transform a legacy system to operate in the cloud.

From a business point of view, there are huge benefits in going serverless rather than instance based (including containers). A very large jump in business agility can be achieved through focusing on the problems and opportunities rather than the technical jungle of traditional computing solutions.

From a technical point of view, it is almost nirvana where you can eliminate many points of failures in the architecture.


“How To Build An Event Store”, Paid Course


Your event store is the heart of an event sourced system. The event store is the source of truth for all business events. It needs to be able capture and replay all domain events in your system reliably and with great performance.

In this course, I will walk you through building an event store that you can re-use in your own projects. In addition, I will walk you through building a read model that allows you to query domain events from the read model.

I will also go through why building your own event store has many more advantages over using a third-party event store.

We will be building the event store in AWS DynamoDB but you can apply the design to a traditional RDMS SQL storage just as well. I will go over the pros and cons in doing so.


“Architecting And Designing Event Based Microservices”, Paid Course


Learn the details on how to design and architect event based microservices using Domain Driven Design (DDD), Event Storming, CQRS, and EventSourcing techniques. I will show you how best combine many principles, patterns, and techniques to create an architecture with as few points of failures as possible and still deliver a great solution.

What you will learn can be applied to cloud based systems but also to traditional, on-premise systems. The benefits are great in either environments.

Whether you are designing a new system in a greenfield environment or transforming a legacy system, I will show tips & tricks that you can use depending which type of project you are in.


“Implementing A Serverless Microservice in AWS”, Paid Course


Learn the details on how to implement a serverless microservice in AWS using Domain Driven Design (DDD), CQRS, and EventSourcing techniques.

We will build a fully functioning billing system in AWS using Visual Studio and C# .NET Core. Even if you are not familiar with C# and .NET Core, you will learn a lot of practical tips on using the different AWS services including building fully automated CI/CD pipelines.


I’m still working on these courses but I’m planning on publishing “Why You Need Serverless Microservices, Yesterday” and “How To Build An Event Store” first.

Updated C# Reference Implementation

I have updated my C# reference implementation and included FluentValidation on some of the DTO objects. I also updated the ErrorMap to include validations on the server side as well as on the WPF client side. This version also includes a sample SQL Server Persistence Provider. As always, you can get the latest code on my GitHub repo.

Object Persistence Reference Implementation

I’ve been updating my reference implementation in the last few days. I’m actually using this reference implement in my own projects. You can download the latest version on my GitHub repo.

This is a complete .NET C# reference implementation to help you jump start a service oriented system running in a cloud environment such as Amazon’s EC2 or on-premis clusters.

This reference implementation shows you how to build a client and the server side. The client side is a sample WPF application that communicates via http REST requests using JSON payloads to the service side. Of course, you can use any type of client as long as the client can communicate via http and REST based JSON’s.

The service side is using a Web API 2 service layer that communicates to a central domain model. The service side demonstrates how to handle exceptions and edge cases and how to communicate failure to the client.

The persistence layer demonstrates the extreamly powerful provider pattern to store the domain objects into the following databases:

  1. db4o (an object database)
  2. Redis (a NoSQL database)
  3. SimpleDB (a NoSQL database)
  4. SQL Server (comming soon)

Please note that the entire system has no knowledge on how the objects are stored. All implementation details are in the individual providers listed above. This means that you can switch the persistence provider without having to recompile and therefore switch a running system from one persistence store to another.

I will try to create a sample SQL Server provider soon.

appsworld North America 2015 at Moscone Center West, San Francisco


I’m a confirmed speaker at the appsworld North America 2015 at Moscone Center West, May 12-13 in San Francisco, CA.  Discover the future of multi-platform apps. See all confirmed speakers. This sure will be an exciting event. I’m still working on my presentation that will include Redis, Amazon AWS, C#, and more. I will see you there.

Presenting “Object Persistence in C#” in Sacramento, CA, March 25th, 2015

Wednesday, March 25th, 20015, I will be presenting “Object Persistence in C#” at the Sacramento .NET User Group (SAC.NET) at the Microsoft Office at 1415 L Street, Suite 200, Sacramento, CA 95814 starting at 6:00 pm. Maria Martinez, Co-Organizer, Sacramento .NET User Group, was kind enough in helping to get this organized. Thank you Maria. I will see you there.

Presenting “Object Persistence in C#” at Bay.NET User Group on April 9th, 2015

I will be presenting “Object Persistence in C#” at the Bay.NET user group at the Berkeley City College located at Room 451A, 2050 Center Street, Berkeley, CA from 6:15 pm – 9:00 pm.

Deborah Kurata, Co-Organizer, East Bay Chapter Leader, was kind enough in helping to get this organized. Thank you Deborah.

I will see you there.

Object Persistence, Part 5 – Video – Redis Provider

In part 4 of this series, I went through the entire Visual Studio solution and also showed the db4o object database provider.

In part 5, I’ll show you how to store your Plan Old C# Objects (POCO) into Redis using the Redis Cloud at redislabs.com service. We will build the Redis Provider and take it out for a spin storing our new domain objects.

You can download the source code at GitHub.

Object Persistence, Part 4 – Video

In part 3 of my Object Persistence series, I introduced the complete Visual Studio 2012 source code.

This is part 4 of my Object Persistence series. I created a detailed video that goes thru all the parts in the solution. Enjoy! Make sure you continue with part 5 where we build a Redis persistence provider.

Watch the video walkthrough on my YouTube channel:

Object Persistence, Part 3 – Source Code

In part 2 of my Object Persistence series, I’ve touched on the issues that still exist today.

In part 3, I’ve published a complete sample Visual Studio 2012 solution on GitHub that demonstrates object persistence using a db4o persistence provider. Over time, I will add additional sample persistence providers for Redis, SQL Server, and possibly a NoSQL provider such as SimpleDB (one of Amazon’s great NoSQL databases).

This sample solution includes complete server side and client side layers. The Server side runs as a REST based Web API 2 service. The server portion also includes a simple domain model and, of course, the persistence provider and how it is implemented. I will update the solution over time, expand the domain model, UI, etc. as required.

The client side is a WPF application that consumes the REST service. The payload to and from the REST service is via JSON objects.


I hope you like it. You can use this sample solution as a template to start simple or very complex software solutions. This solution can easily be taken and split across different nodes in a cluster of Amazon AWS EC2 instances, for example. However, for a cloud based solution, your persistence would have to support certain features. I will go into details when I add the Redis persistence provider.

Instead of writing a very long blog post, I will post a screen cast video and go through the solution. I think this will make more sense and you have a chance to go through the source code with me. So, go ahead and get the latest version from GitHub and start playing with it.