Moved a Core Web Vitals collection setup designed for shared observability infrastructure to my personal blog. Fixed a dashboard left empty by sparse traffic and changed when metrics are collected for ordinary browsers. This post records the changes from October 17 to 22, query omissions investigated on October 23, and what five days of data can support.
Sent the Core Web Vitals measured in an app webview to an observability platform shared by many teams. The webview gave no signal on leaving, and tail sampling, delta-to-cumulative conversion and Tempo queries each dropped values in their own way without raising an error. For every setting that could not be changed, re-measured what was lost in a reproduction environment.
A feature where the server opens a URL the user handed it has the textbook conditions for SSRF written into its spec. Six ways a whitelist gets bypassed first, then five defensive principles that block them, all actually run on Node. Strip IPv4-mapped by hand and it gets through in hex notation, undici lookup hook is never called when the host is an IP literal, and URL.hostname keeps the brackets on an IPv6 literal. The final post of a two-part design note on OG scraping servers.
The "10% error rate" of a link preview server is a single number that five different kinds of failure got mashed into. This post works out why this workload is I/O bound at that TPS, where runtime choice actually diverges across four points, and then moves on to lowering the error rate with User-Agent and encoding. Node built-in TextDecoder turns CP949 extension characters into different characters without raising an error, and a scraped og:title is not an API response but user input. It also covers cache stampedes, negative caching, and a two-million-run simulation that verifies "P95 under one second" by working backwards from the cache hit rate. The first post of a two-part design note on OG scraping servers.
Raise traffic 12x and it takes 31.5 seconds for a new pod to receive its first request. I pulled an itemized bill for those 31.5 seconds with a stopwatch: the structure dominated by the detection window, the conditions under which the autoscaler goes blind in the five minutes right after a deploy, the scale-down staircase, why memory-based HPA misfires on Node, and KEDA's preemptive scaling. Part 5 of the Kubernetes for frontend developers series.
Build-time transformations, cache key serialization, ResumeDataCache, cacheHandler, and Cache Components - everything created by a single 'use cache' line
The uncomfortable truth benchmarks reveal
What question does vinext really ask?
Hey Edge Middleware, how have you been?
What happens behind a single line of "use server"?
A preview of section 5.2 (Pitfalls of the vm Module) from the upcoming Node.js Deep Dive book.
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How to survive when JSON.parse() becomes overwhelming
CVE-2025-55182, CVE-2025-55184, CVE-2025-55183, and the React hidden inside Next.js
A look at V8's generational garbage collection, adjusting heap memory limits, and practical ways to diagnose memory leaks.
Why GitHub Actions scheduled workflows get delayed by dozens of minutes: the structural causes, and free alternatives that actually run on time.
