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Derek Comartin

AVOID Entity Services by Focusing on Capabilities

Entity Services are services that are centered around an Entity. For example, a CustomerService or a ProductService. Most times these services focus on data and CRUD operations. These services can cause low cohesion and in turn cause high coupling. Instead, focus on capabilities of services, the data encapsulated and owned by the service. Focusing on capabilities will increase cohesion and lower coupling. YouTube Check out my YouTube channel where I post all kinds of content that accompanies my posts including this video showing everything that is in this post. Entity Services I believe that the default way that systems are built and… Read More »AVOID Entity Services by Focusing on Capabilities

Projections in Event Sourcing: Build ANY model you want!

Projections in Event Sourcing are a way to derive the current state from an event stream. This can be done asynchronously as events are persisted to an event stream which can update a projection. You don’t need to replay all the events in an event stream to get to the current state for a UI every time you need to display data. This could be very inefficient if you have a lot of events in a stream. Rather, create a projection that represents the current state and keep it updated as events occur. YouTube Check out my YouTube channel where I post… Read More »Projections in Event Sourcing: Build ANY model you want!

Event Sourcing Example & Explained in plain English

What is Event Sourcing? It’s a way of storing data that is probably very different than what you’re used to. I’ll explain the differences and show ab event sourcing example that should clear up all the mystery around it. YouTube Check out my YouTube channel where I post all kinds of content that accompanies my posts including this video showing everything that is in this post. Source Code Developer-level members of my CodeOpinion YouTube channel get access to the full source in this post available in a git repo. Check out the membership for more info. Current State The vast majority of… Read More »Event Sourcing Example & Explained in plain English