Next.js App Router: what I would tell my past self

Server components are the default — treat them that way

Most of my early mistakes came from reaching for "use client" too soon. Data belongs on the server; interaction belongs on the client; the boundary should be as low in the tree as possible.

Caching: know which layer you are in

The three mistakes I made on a paid project and what each one cost, written up in the finished version of this post.

What I would tell my past self

Read the routing and caching docs once, end to end, before the first commit.