Proxy cache basics in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this Nginx cache status header?

You have configured Nginx with proxy_cache and added the header X-Cache-Status to responses. After a client requests a cached resource twice, what will be the value of X-Cache-Status in the second response?

Nginx

proxy_cache_path /tmp/cache levels=1:2 keys_zone=mycache:10m max_size=1g inactive=60m;
server {
    location / {
        proxy_cache mycache;
        proxy_pass http://backend;
        add_header X-Cache-Status $upstream_cache_status;
    }
}

A "EXPIRED"

B "MISS"

C "HIT"

D "BYPASS"

💡 Hint

Think about what happens when a cached response is served again.

The first request will be a MISS because the cache is empty. The second request will be served from cache, so the header will be HIT.

❓ Configuration

intermediate

Which configuration snippet correctly sets up proxy cache with a 30-minute inactive timeout?

You want to configure Nginx proxy cache to store cached files and remove them if they are not accessed for 30 minutes. Which snippet correctly sets this?

A proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=cache_zone:10m max_size=500m inactive=30m;

B proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=cache_zone:10m max_size=500m inactive=30s;

C proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=cache_zone:10m max_size=500m inactive=30h;

D proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=cache_zone:10m max_size=500m inactive=300m;

💡 Hint

The inactive parameter uses time units like s, m, h for seconds, minutes, hours.

The inactive=30m means cached files not accessed for 30 minutes will be removed. Other options use wrong units or too long/short times.

❓ Troubleshoot

advanced

Why does Nginx not cache responses despite proxy_cache configured?

You configured proxy_cache in Nginx, but responses are never cached. Which reason below explains this behavior?

A The proxy_cache_valid directive is set to 0.

B The backend server sends Cache-Control: no-store header.

C The proxy_pass URL is incorrect.

D The proxy_cache_path directive is missing.

💡 Hint

Check what response headers from backend can prevent caching.

If backend sends Cache-Control: no-store, Nginx will not cache the response regardless of proxy_cache settings.

🔀 Workflow

advanced

What is the correct order of steps to enable proxy caching in Nginx?

Arrange these steps in the correct order to enable proxy caching in Nginx.

A 1,2,3,4

B 2,1,3,4

C 1,3,2,4

D 3,1,2,4

💡 Hint

Think about defining cache first, then enabling it, then proxying, then headers.

First define cache path, then enable cache in location, then set proxy_pass, finally add headers.

✅ Best Practice

expert

Which option is the best practice to avoid caching sensitive user data in Nginx proxy cache?

You want to ensure Nginx proxy cache does not store responses containing sensitive user data. Which configuration is best?

A Use proxy_cache_lock to prevent multiple cache writes.

B Set proxy_cache_valid 0 for all responses.

C Disable proxy_cache entirely.

D Use proxy_cache_bypass with a condition checking for cookies indicating logged-in users.

💡 Hint

Think about bypassing cache selectively based on user state.

Using proxy_cache_bypass with conditions like checking cookies allows caching public content but bypasses cache for logged-in users, protecting sensitive data.