Purging cached content in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this command to purge cache in Nginx?

You run the following command to purge a cached file in Nginx cache directory:

rm -rf /var/cache/nginx/*

What is the expected result?

Nginx

rm -rf /var/cache/nginx/*

A The command deletes only files named '*' literally.

B Only cached files older than 7 days are deleted.

C The command returns an error because of missing sudo privileges.

D All cached files in /var/cache/nginx/ are deleted immediately.

💡 Hint

Think about what the wildcard * means in shell commands.

The rm -rf command with * deletes all files and folders inside the specified directory immediately. No age filtering happens.

❓ Configuration

intermediate

Which Nginx configuration snippet enables cache purging via HTTP request?

You want to allow cache purging by sending a special HTTP request to Nginx. Which configuration snippet correctly enables this?

Nginx

location ~ ^/purge(/.*) {
    allow 127.0.0.1;
    deny all;
    proxy_cache_purge my_cache $1;
}

A

location ~ ^/purge(/.*) {
    allow 127.0.0.1;
    deny all;
    proxy_cache_purge my_cache $1;
}

B

location /purge/ {
    proxy_cache_purge my_cache $request_uri;
    allow all;
}

C

location /purge/ {
    deny 127.0.0.1;
    allow all;
    proxy_cache_purge my_cache $request_uri;
}

D

location /purge/ {
    proxy_cache_bypass my_cache $request_uri;
    allow 127.0.0.1;
    deny all;
}

💡 Hint

Remember to restrict purge access to localhost only.

Option A correctly restricts purge access to localhost and uses proxy_cache_purge directive.

❓ Troubleshoot

advanced

Why does the cache not purge after sending a PURGE request?

You configured Nginx to allow PURGE requests to clear cache, but after sending a PURGE request, the cache remains. What is the most likely cause?

A The PURGE request was sent from an unauthorized IP address.

B The cache directory is empty, so nothing to purge.

C The PURGE method is not allowed in the Nginx configuration.

D The proxy_cache_path directive is missing.

💡 Hint

Check IP restrictions in your purge location block.

If the PURGE request comes from an IP not allowed by 'allow' directive, Nginx denies it silently, so cache is not purged.

🔀 Workflow

advanced

What is the correct workflow to safely purge a specific cached URL in Nginx?

You want to purge the cached content for URL /images/logo.png without affecting other cached files. What is the correct sequence of steps?

A 2,4,1,3

B 2,1,3,4

C 1,2,3,4

D 4,2,1,3

💡 Hint

Think about verifying config before purging and checking logs after.

First verify cache key (2), then send PURGE (1), check logs (3), and reload config last if needed (4).

✅ Best Practice

expert

Which practice is best for purging cached content in a high-traffic Nginx environment?

In a busy production environment, what is the best practice to purge cached content without causing downtime or performance issues?

A Disable caching temporarily during purging to avoid stale content.

B Manually delete all cache files daily with rm -rf to ensure freshness.

C Use HTTP PURGE requests restricted by IP and automate purging only for changed URLs.

D Reload Nginx after every PURGE request to apply changes immediately.

💡 Hint

Think about minimizing impact and targeting only needed cache entries.

Option C minimizes impact by purging only changed URLs via controlled HTTP PURGE requests, avoiding downtime.