Blog

The EventEmitter pattern lets components in the same process react to the same event without being directly coupled — no message broker needed.

One file to guard every route — plus the Next.js 16 rename that moves it off the Edge runtime, the request-vs-response header trap that leaks user IDs to the browser, and the CVE that explains why this can never be your only auth layer.

Parallel routes let a single layout render multiple independent pages at once. Combine them with intercepting routes and you get URL-aware modals with zero hacks.

Node.js runs on one CPU core by default. The cluster module lets you fork N workers across all cores — here's the pattern, graceful shutdown, IPC, and when PM2 makes it unnecessary.

Server Actions collapse form handling into a single server function—no API route, no manual fetch, no useState for loading. Here's the pattern that replaces 80% of your mutation boilerplate.

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.