I’ve spent four years running WordPress at scale on Altis Cloud. I expected the biggest lessons to be about infrastructure, but looking back, they were really about good engineering habits: treating assumptions as a starting point (not a conclusion to defend), doing the unglamorous work that makes systems resilient, and following problems beyond the boundaries of what you strictly need to know.
Through real incidents and experiences, this talk explores how challenging assumptions, learning fully from failure, and understanding the wider system lead to better decisions. These lessons were learned at scale, but they are useful to engineers working with systems of any size.