Error Autopsy
The Cache Stampede the Second the Key Expired
One popular key expired and four hundred requests missed at the same instant, so all four hundred rebuilt the value, and the database took the whole load at…
Latest
Deep Dive
Why AI-Written Code Is Shaped Like the Happy Path
Generated code reflects the distribution it was trained on, and that distribution is tutorials and working examples, so the edges are where generated code…
Deep Dive
What the Cache Headers Actually Mean, and Which One Wins
Four headers set the caching behaviour and they disagree, so the effective policy is a precedence order rather than a sum, and the order is not what the…
Shopify
A Performance Budget That Survives Contact With a Real Store
Performance work that is not enforced gets undone within a quarter. Here is the budget I use, the numbers behind each limit, and how to fail a build on it.
Tooling
The strace Output That Showed the File Was Never Opened
The config was ignored and the logs said nothing, and the syscall trace showed the open call failing on a path that differed by one character from the path…
Security
The Model Output That Rendered as HTML in the Browser
The assistant's reply was trusted because a model wrote it, and the reply was inserted with innerHTML, so a crafted input became stored script, and the…
Shopify
Your Theme Has 340 Settings and Merchants Use Eleven of Them
Every setting is a conditional in Liquid, a branch in CSS and a support question. I counted what a real theme actually used, and the answer changed how I…
Shopify
The Theme JavaScript That Blocked Rendering for 1.2 Seconds
One script tag without defer, loading a bundle nothing above the fold needed. How to find what is blocking your paint and what each fix actually changes.
Shopify
The Announcement Bar That Cost 0.31 CLS
Every element on the page moved down 44 pixels, a third of a second after paint. Finding the culprit took one API and a screen recording.
DevOps
The Liveness Probe That Killed the App When the Database Was Slow
The probe queried the database, so the slow database made the app look dead, and the restarts made the database slower, and the loop ran until someone read…
Shopify
How to Tell Which App Is Actually Slowing Your Store Down
Uninstalling apps one at a time and re-running Lighthouse is not a method. Here is how to attribute main thread time and bytes to a specific app in one pass.
Shopify
Your Lazy-Loaded Hero Image Is Why LCP Is Four Seconds
Someone added loading lazy to every image in the theme, including the one the browser needs first. Here is how the biggest LCP regression I have seen was…