Nginx

Nginx is usually the layer sitting in front of whatever I've actually built. I used it as a reverse proxy and TLS terminator, routing requests to the right backend service, serving static assets directly, and keeping certificates and redirects sane.

It showed up wherever my older projects needed a front door. Proxying to the backend and generally being the piece that makes "it works from the browser" actually true.

It's not glamorous, but a misconfigured proxy will ruin your day faster than almost anything else, so I've gotten precise about it. (Believe me, I setup Nginx more often than I want to admit)