Software architect. Author of Event Sourcing & CQRS. DDD, .NET, and legacy modernization. Founder, Legacy to Modern.
Joined January 2009
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My book, Event Sourcing & CQRS, is planned for November 1.
When to use it, how to build it in .NET, and how to migrate an existing system.
The companion code is public now. I'll add Amazon links here when available:
legacytomodern.com/event-sou…
ALT Cover of Event Sourcing & CQRS by Thomas Jaeger
1/ My book is out. Event Sourcing & CQRS is on Amazon in Kindle, paperback, and hardcover. 18 chapters, 72 diagrams, and a public .NET 10 reference implementation with four event stores behind one interface.
amazon.com/dp/B0HNV5F4GX
4/ The code runs on PostgreSQL, SQL Server, KurrentDB, and DynamoDB, and all four pass the same contract test suite. Five bounded contexts, event-sourced process managers, eight projections, tenant isolation, and more than fifty decision records. MIT.
github.com/ThomasJaeger/even…
1/ The manuscript is finished.
452 pages. 18 chapters. 72 diagrams. 79 code listings.
More useful to you: the reference implementation it was built on is now public.
6/ On the book: it is in submission. No publisher named, no date, and I am not inventing one.
Manuscript finished is a fact. A publication date is not yet a fact.
Clone it. Tell me where it is wrong
Correction. The paperback and the hardcover are scheduled for November 1, 2026, self-published on Amazon. Both are 448 pages, 7 by 10. The code is public now.
legacytomodern.com/event-sou…
If the system is yours, the hour is here. legacytomodern.com/book
Two shopping carts. Customer A adds 3 items and checks out. Customer B adds 4, winces at the total, removes one, checks out. In your CRUD database the two orders are now byte-for-byte identical.
The removed item was deferred desire. A future sale. Marketing gold. The schema had nowhere to put it, so a DELETE erased it, and nobody in the business was ever asked.
Greg Young's point from his Code on the Beach talk still lands a decade later: update-in-place systems destroy information all day, silently. Event sourcing is the model that does not.
youtube.com/watch?v=JHGkaSho…
I can tell in ten minutes whether a team has really understood Event Sourcing.
Not from their event store. From whether they can keep commands and domain events apart.
My check: who is allowed to say no?
Nobody? Event. One thing? Command. A subscriber? You've built a distributed bug.
Two years ago I started outlining a book on event sourcing and CQRS and kept stalling. What unlocked it: build the implementation first, let the code tell you what the book says.
449 pages later, every chapter that disagreed with the code got rewritten. The code was right every time.
Just dropped my latest video: "AI is a TOOL. Architecture is a Vision." youtu.be/nA9QBUCPzkQ?si=pZSu…
#SoftwareArchitecture #EventSourcing #AI
#Python is 72x slower and uses 76x more energy than C. I'm not surprised at all. Have a look: thomasjaeger.wordpress.com/2…
I'm excited to announce my new course on Udemy: Build an Event Store in C# .NET for CQRS and Event Sourcing udemy.com/course/build-an-ev…
