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Web / NGINX Interview questions

Define upstream in NGINX?

An upstream block defines a named group of one or more backend servers that NGINX can proxy requests to. It's declared at the http level and referenced by name inside a proxy_pass directive.

upstream backend_app {
    server 10.0.0.11:8080;
    server 10.0.0.12:8080;
}

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

Beyond listing servers, the upstream block is where load-balancing algorithm, weights, and health-check-related parameters like max_fails and fail_timeout are configured.

An upstream block is referenced elsewhere in the config using which directive?
Besides listing backend servers, what else can an upstream block configure?

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