DDD Europe 2023 - Program

Beyond Aggregates: Advanced patterns for use with Event Sourced systems

EventSourcing Live - EventSourcing Live Talk (50m)


James Geall

James Geall
Wednesday 7 from 11:55 until 12:45 in Blue Room

There are a set of simple rules for building event sourced Aggregates that work quite well, in most cases. However, there are a handful of common business cases that when implemented using these rules generate a tangled mess of accidental complexity. One advanced pattern that can help in these situations is the process manager. Understanding when to use them, how to build them and the trade-offs that are being made can be critical to succeeding.

This talk will give attendees with an understanding of what process managers are, when to use them, how to build them and pitfalls that can cause problems. Code examples of both business and technical problems that process managers can help solve will help reinforce these ideas with stripped down implementations from systems currently in production.


An understanding of Event sourcing and how aggregates work is necessary as is familiarity with at least one Object Oriented or Functional programming. Some familiarity with integration patterns is useful but not required as those covered will be explained.

About James Geall

Twitter LinkedIn Company Website

Over 2 decades of distributed programming experience with a focus on messaging and 12+ years in the Event Sourcing/DDD space. Multiple event-sourced systems in production across a variety of business verticals including Pharmaceutical, Finance and Logistics. I currently work for Event Horizon Consulting delivering training on advanced DDD, CQRS and Event Systems.