Performance
The Font Swap That Moved the Button Mid Click
Swap fixed the invisible text and introduced the layout shift, and the shift landed on the checkout button at the moment of the click, so the user tapped…
Opinion
Fast Is a Feature, and a Feature Needs an Owner
Performance regresses by accretion, one reasonable change at a time, because nobody owns the budget, and a property with no owner is a cost with a deadline.
Deep Dive
How a Single Lost Packet Becomes Your p99
A dropped segment is not retried immediately. The retransmission timer backs off exponentially, so one loss adds a stall measured in round trips squared…
Shopify
Infinite Scroll Made the Collection Page Slower With Every Scroll
By the fifth batch the page held 240 product cards and dropped frames on every scroll. The DOM node count was the metric nobody was watching.
Shopify
Tapping a Variant Took 480ms to Do Anything
INP replaced FID and it is much harder to pass. A variant selector that felt fine on a laptop was failing badly on the phones customers actually use.
Shopify
Why render Is Faster Than include, and Its Real Cost
Shopify deprecated include for a reason that is about scope, not syntax. The performance difference is real and the migration breaks things in a predictable…
DevOps
The Autoscaler That Scaled on a Metric That Lagged the Traffic
The HPA added pods after the spike had passed and removed them after the next one began, because its metric was smoothed, delayed and averaged.
Performance
The Next.js Page That Shipped the Database Client to the Browser
The page weighed two megabytes and the network tab showed a database driver going to the browser. A server only import crossed the boundary through one…
Deep Dive
How Cloudflare Freed 100 TB by Deleting 64 Bytes at a Time
Five successive changes to a Rust cache entry took it from 953 bytes to 420 across 250 billion entries, and made lookups 19 percent faster rather than slower.
Performance
The Third Party Script That Held the Main Thread Hostage
First paint waited on a vendor's deploy, because a synchronous tag manager script blocked the parser, and its long tasks queued every interaction behind…
Deep Dive
The Checkpoint Storm That Spiked Latency Every Few Minutes
Latency was fine, then terrible, then fine, on a rhythm of a few minutes, with no traffic rhythm to match. The period was the checkpoint interval, and the…
Tooling
Reading a HAR File Like a Flight Recorder
The browser recorded the entire incident, every request, every wait, every byte, before anyone knew there was one.