Your parents flew to Split for their summer holiday. They went to Yugoslavia. Yugoslavia doesn't exist any more, so why does your flight tracker insist they went to Croatia?

That's the question that made me realise my nice, simple CRUD database had quietly stopped being simple. Airlines merge and rebrand. Airports get renamed, and sometimes change country. Borders move. A row that just says "Croatia" rewrites my parents' holiday every time the world does.

This is the story of how a hobby flight logger outgrew its schema, and what event sourcing actually looks like once you build it instead of reading blog posts about it. No Kafka, no swarm of microservices: just Symfony, Doctrine, Messenger and a few hundred lines of PHP. We'll go through the parts that matter (append-only events, projections, and the temporal queries that let me ask "what country was this on the day of the flight?") using real, messy aviation data.

And if your parents holidayed in Yugoslavia too, you're in the right room.