Ismael Celis

This blog post is only incidentally about AI.

I’ve kept talking about command-driven and event-sourced apps in Ruby, to anyone who’ll listen.

For a number of years now, I’ve been hacking on several side-projects in parallel, whenever I can.

Watch the talk on YouTube I gave a talk at Wroclove.rb, in Poland, this April.

This is a presentation about durable messaging, Event Sourcing and Ruby that I gave at the London Ruby User Group this past November.

The conventional distinction between “foreground” request handling and “background” operations in web development is broken, misleading, and incomplete.

Video of a presentation on Ruby and Event Sourcing I gave at Baltic Ruby 2025 back in June.

Things I’ve said on Bluesky in August 2025.

In Object Oriented programming, identity and behaviour are often conflated.

Our experience of reality is based on the passage of time.

I was recently invited to chat at the Dead Code podcast (thank you for the invite!)

I’ve been playing with and exploring Event Sourcing for a while now, but only recently realised that part of my thinking might have been muddled by unexamined assumptions about what commands are and what they do in the context of Event Sourcing.

The Decide, Evolve, React pattern provides a unified mechanism for expressing, handling and reacting to state changes in a system.

In this series: Part 1: Practical Railway-Oriented Pipelines in Ruby Part 2: User input, errors and metadata Part 3: Extending pipelines Part 4: Middleware Part 5: Testing pipelines Testing pipelines.

In this series: Part 1: Practical Railway-Oriented Pipelines in Ruby Part 2: User input, errors and metadata Part 3: Extending pipelines Part 4: Middleware Part 5: Testing pipelines In the previous article in this series I showed how to extend the basic p…

In this series: Part 1: Practical Railway-Oriented Pipelines in Ruby Part 2: User input, errors and metadata Part 3: Extending pipelines Part 4: Middleware Part 5: Testing pipelines In the previous article in this series I showed how to pass extra metadata

In this series: Part 1: Practical Railway-Oriented Pipelines in Ruby Part 2: User input, errors and metadata Part 3: Extending pipelines Part 4: Middleware Part 5: Testing pipelines In the previous article I described a bare-bones implementation of Railwa…

In this series: Part 1: Practical Railway-Oriented Pipelines in Ruby Part 2: User input, errors and metadata Part 3: Extending pipelines Part 4: Middleware Part 5: Testing pipelines Some years ago I explored patterns for building composable processing pip…

This is part of a series on Event Sourcing concepts, with Ruby examples.

This is part of a series on Event Sourcing concepts, with Ruby examples.

In this series I’ll go over the basic concepts in Event Sourcing.

An exploration of patterns for building composable data pipelines in Ruby, from the basics to the possibly YAGNI.