Event sourcing is a hot topic (well, it's heating up). Kickstarter's engineering team decided to dive in and build their next product with a home-grown event sourced approach.
Author Philippe Creux compares event sourcing to Git:
Most software developers use a tool to keep track of code history. Git is a fantastic example that’s used widely across the industry. Type git log and you can see all the changes made to a codebase. Who made the change, when it happened, what the change was, why the change was made and how the change was performed. Git is also a time machine, that allows you to go back in time and see what the code looked like back then. You can also replay history and play what-if scenarios: go back in time, checkout a new branch, commit a change, and replay all the events commits that happened after that.
A more formal definition by Martin Fowler is:
All changes to an application state are stored as a sequence of events
The article serves as a hands-on guide to build a pragmatic event sourced system. It's an interesting topic for both back- and frontend developers. If you're a frontend developer, you might already be applying event sourcing ideas with state management libraries like Redux.