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Web / NGINX Interview questions

What is the difference between proxy_pass and rewrite in NGINX?

proxy_pass and rewrite solve different problems, even though both can change where a request ends up.

proxy_pass forwards a request to a different server entirely - the URL the client sees stays the same, but NGINX acts as an intermediary passing the request to an upstream application, which returns a response NGINX relays back.

location /api/ {
    proxy_pass http://backend_app;
}

location /old-path/ {
    rewrite ^/old-path/(.*)$ /new-path/$1 permanent;
}

rewrite, by contrast, modifies the request URI itself, either internally (continuing processing with the new URI) or by issuing an HTTP redirect back to the client. It doesn't involve a backend server at all - it's pure URL manipulation within NGINX.

Confusing the two is a common mistake: using rewrite when you actually need to forward to another service, or using proxy_pass when you just need to change a URL path.

Which directive forwards a request to an entirely different backend server?
What does the rewrite directive operate on?

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