Offset 0: why this notebook exists

Every week I solve problems people search for at two in the morning without finding a complete answer: a Debezium connector that stops with no clear error, a Kafka consumer stuck in a rebalancing loop, a Patroni failover that does not go as planned. I also prepare courses, slides and animations to explain these mechanisms to my students.

Until now, all of that stayed in conversations, tickets and course folders. This notebook is a way to make it useful to others.

What you will find here

• Notes: a real problem, what we were seeing, the hypotheses in order (including the wrong ones), the fix and what to take away from it.
• Slides: my course and talk material, readable directly in the browser.
• Labs: animations and interactive experiments, to understand a mechanism by playing with it rather than reading about it.

How every entry is written

I work with Claude a lot. When a session ends with something worth sharing, I ask it to draft an entry in French and English. The draft is anonymised: no client names, no real addresses or configuration, no secrets. It then arrives as a pull request on the site’s repository, and nothing goes live until I have read and approved it.

The goal is simple: publish regularly without giving up what makes a technical note valuable, which is the real reasoning behind the fix.

Why the numbers

Every entry has a number, like a message in a Kafka partition: the first one is offset 0, and a number is never reused. On the home page, the log shows every entry in order, and the ones you have already read are filled in.