I can answer some of your questions about EventStoreDB. Is it a clustered/replicated database? Yes, the ESDB cluster is a single-leader replica set like MongoDB. How does it scale (both compute and storage) horizontally? No, and it's by design. ESDB has a single log, so all the events for the…

The Aggregate pattern is probably the most important tactical pattern in Domain-Driven Design (DDD). In essence, it could be described like this: An aggregate is a cluster of domain objects that can be treated as a single unit. This means that the objects within an aggregate are closely related and…

I finally opened a YouTube channel for Eventuous. The first video published there is the one that I call “The power of the transient state”. Here is a summary of the video. In an event-sourced system, you don’t need to keep the entity state in any database as a…

I started working on Eventuous, a set of libraries for .NET that help people to start building event-sourced systems, in January 2021. Fifteen months ago, on 25 March 2021, the first version (0.1.0) found its way to NuGet. What happened between then and now? As I write this post, Eventuous…

Eventuous is an OpenSource Event Sourcing library for .NET. Read mode at https://eventuous.dev All the versions of Eventuous before 0.10 had the aggregate identity as part of the aggregate state by default, you weren’t able to avoid having it there. As a developer, you were also required to set the…

In event-sourced systems, the domain model is using events as the source of truth. These events represent individual and atomic state transitions of the system. We add events to the event store one by one, in an append-only fashion. When restoring the state of an aggregate, we read all the…

What is Eventuous Connector and how to use it Eventuous connectors allow subscribing to events from EventStoreDB (source) and produce derived events to another system (sink). Some sinks also support reduce-like operations that work as projections. The Connector is a combination of a real-time subscription (currently only to $all stream)…

Real-time subscriptions are essential when building a successful event-sourced system. They support the following sequence of operations: The domain model emits a new event The event is stored in the event store The command is now handled, and the transaction is complete All the read models get the new event…