Built-in APIs

Core `node:` modules every backend uses daily.

Filesystem paths vs WHATWG URLs - different tools for different jobs.

`setTimeout`, `setInterval`, `timers/promises`, and scheduling primitives.

Async files, streams, flags, and watching - the filesystem surface.

`util.promisify`, `inspect`, `debuglog`, and Node 24 helpers.

Hashing, HMAC, random bytes, and modern cipher APIs.

Host info, env, memory, CPU, and process metadata.

Reach for `node:` built-ins before npm; know promise vs sync APIs.