[nginx] Nginx -- static file serving confusion with root & alias

In your case, you can use root directive, because $uri part of the location directive is the same with last root directive part.

Nginx documentation advices it as well:
When location matches the last part of the directive’s value:

location /images/ {
    alias /data/w3/images/;
}

it is better to use the root directive instead:

location /images/ {
    root /data/w3;
}

and root directive will append $uri to the path.