Blog

Four caching layers, three revalidation APIs, and the Next.js 16 rename that turns everything you learned in 15 into the "previous model". Here's the complete mental model for data fetching in the App Router.

You have a UserService that needs a Database. Your OrderService needs UserService, Database, and a PaymentGateway. Your NotificationService needs EmailClient and UserService.

One call with the wrong argument type, made once, makes the next 100 million integer additions roughly 3x slower. Hidden classes, inline caches, the tier-up thresholds and every deopt reason — checked against what Node 22 actually does, not what the blog posts say.

The Two Sum problem is the "Hello World" of hash map problems. Most people solve it, move on, and treat it as a warmup. That's a mistake. The pattern behind Two Sum — trading space for lookup speed — shows up in dozens of harder problems.

Most Node.js services drop in-flight requests on every deploy. Here's the complete pattern: SIGTERM handling, HTTP draining, queue cleanup, and Kubernetes integration.

Build a pub/sub system from 60 lines of JavaScript: subscribe, publish, unsubscribe, once(), namespace wildcards, error isolation, and async publish.

Awaiting four independent API calls in sequence instead of parallel can triple your endpoint latency. Here's the pattern, the math, and how to catch it in review.

You've read "Node.js is single-threaded and non-blocking." Fine. But that sentence raises more questions than it answers. If it's single-threaded, who's doing the file I/O while your JavaScript runs?

Strip Express and Koa down to their core: a 30-line compose() function that chains async middleware with before/after hooks, short-circuit support, and error propagation.