Web server vs application server in Nginx - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Role of Nginx as a Web Server

Which statement best describes the primary role of Nginx when used as a web server?

A It serves static content and forwards requests to application servers.

B It processes business logic and runs application code directly.

C It stores data and manages database transactions.

D It compiles source code into executable programs.

💡 Hint

Think about what a web server does when a user visits a website.

Nginx as a web server mainly serves static files like images and HTML. It also forwards dynamic requests to application servers that handle the business logic.

💻 Command Output

intermediate

Nginx Configuration for Proxying Requests

Given the following Nginx configuration snippet, what will be the result when a client requests /app?

Nginx

location /app {
    proxy_pass http://127.0.0.1:8080;
}

A Nginx forwards the request to an application server running on localhost port 8080.

B Nginx returns a 404 Not Found error for /app requests.

C Nginx serves the request directly from its own files under /app.

D Nginx blocks the request due to missing permissions.

💡 Hint

Look at the proxy_pass directive and its target address.

The proxy_pass directive tells Nginx to forward matching requests to the specified backend server, here at localhost port 8080.

❓ Troubleshoot

advanced

Diagnosing 502 Bad Gateway Error

When Nginx is configured to proxy requests to an application server, clients sometimes get a 502 Bad Gateway error. What is the most likely cause?

A Nginx configuration file has a syntax error causing it to fail starting.

B Nginx is serving static files but the files are missing.

C The client sent a malformed HTTP request that Nginx rejected.

D The application server is not running or not reachable at the proxy address.

💡 Hint

Think about what happens if Nginx cannot connect to the backend server.

A 502 Bad Gateway error means Nginx tried to contact the application server but failed, often because the server is down or unreachable.

🔀 Workflow

advanced

Setting Up Nginx as Reverse Proxy for Application Server

Which sequence correctly describes the steps to configure Nginx as a reverse proxy for an application server running on port 5000?

A 1,2,4,3

B 4,1,2,3

C 1,4,2,3

D 2,1,4,3

💡 Hint

Think about installing software before configuring it and starting services.

You first install Nginx, then start the application server, configure Nginx to proxy requests, and finally restart Nginx to apply changes.

✅ Best Practice

expert

Optimizing Nginx and Application Server Setup

Which practice improves performance and reliability when using Nginx as a web server in front of an application server?

A Serve all dynamic content directly from Nginx without forwarding to the application server.

B Use Nginx to serve static files and cache responses from the application server.

C Disable keep-alive connections between Nginx and the application server to reduce resource use.

D Run the application server on the same port as Nginx to simplify configuration.

💡 Hint

Consider how caching can reduce load and speed up responses.

Serving static files with Nginx and caching dynamic responses reduces load on the application server and improves response times.

Practice

1. What is the primary role of a web server like nginx?

easy

A. To deliver static files like images and HTML directly to users

B. To execute backend application logic and generate dynamic content

C. To store user data and manage databases

D. To compile source code into executable programs

Solution

1. Step 1: Understand the role of a web server

   A web server mainly serves static content such as images, HTML, CSS, and JavaScript files directly to users.

2. Step 2: Differentiate from application server

   An application server runs backend code to create dynamic content, which is different from a web server's role.

3. Final Answer:

   To deliver static files like images and HTML directly to users -> Option A

4. Quick Check:

   Web server = static file delivery [OK]

Hint: Web servers serve files; app servers run code [OK]

Common Mistakes:

• Confusing web server with application server
• Thinking web server runs backend logic
• Assuming web server manages databases

2. Which nginx configuration snippet correctly forwards requests to an application server on port 3000?

easy

A. location / { root http://localhost:3000; }

B. location / { fastcgi_pass http://localhost:3000; }

C. location / { proxy_pass http://localhost:3000; }

D. location / { redirect http://localhost:3000; }

Solution

1. Step 1: Identify correct directive for forwarding

   The proxy_pass directive is used in nginx to forward requests to an application server.

2. Step 2: Check other options for correctness

   root serves static files, fastcgi_pass is for FastCGI servers, and redirect sends HTTP redirects, not proxying.

3. Final Answer:

   location / { proxy_pass http://localhost:3000; } -> Option C

4. Quick Check:

   Use proxy_pass to forward requests [OK]

Hint: proxy_pass forwards; root serves static files [OK]

Common Mistakes:

• Using root instead of proxy_pass for forwarding
• Confusing fastcgi_pass with proxy_pass
• Using redirect which changes URL instead of proxying

3. Given this nginx config snippet, what happens when a user requests /app?

location /app {
  proxy_pass http://127.0.0.1:8080;
}

medium

A. nginx serves static files from /app directory

B. nginx forwards the request to the application server at 127.0.0.1:8080

C. nginx returns a 404 error

D. nginx redirects the user to http://127.0.0.1:8080/app

Solution

1. Step 1: Analyze the proxy_pass directive

   The proxy_pass directive tells nginx to forward matching requests to the specified backend server.

2. Step 2: Understand request handling

   Requests to /app are sent to the application server at 127.0.0.1:8080, not served as static files or redirected.

3. Final Answer:

   nginx forwards the request to the application server at 127.0.0.1:8080 -> Option B

4. Quick Check:

   proxy_pass forwards requests to backend [OK]

Hint: proxy_pass means forward, not serve or redirect [OK]

Common Mistakes:

• Thinking nginx serves static files here
• Confusing proxy_pass with redirect
• Assuming 404 error without backend

4. You configured nginx to forward requests to an application server using:

location /api {
  proxy_pass http://localhost:5000/api;
}

But requests to /api/users fail. What is the likely problem?

medium

A. nginx cannot forward requests to localhost

B. The location block should be location /api/ with trailing slash

C. proxy_pass must use HTTPS instead of HTTP

D. proxy_pass should be http://localhost:5000/ without /api

Solution

1. Step 1: Understand proxy_pass URI behavior

   When proxy_pass includes a URI (like /api), nginx replaces the matching part of the request URI with that URI, causing duplication.

2. Step 2: Correct proxy_pass to avoid URI duplication

   Removing /api from proxy_pass (using http://localhost:5000/) forwards the full original URI correctly.

3. Final Answer:

   proxy_pass should be http://localhost:5000/ without /api -> Option D

4. Quick Check:

   proxy_pass URI affects request path [OK]

Hint: Avoid URI in proxy_pass to prevent path duplication [OK]

Common Mistakes:

• Including URI in proxy_pass causing double paths
• Thinking HTTPS is required for localhost
• Believing nginx can't proxy localhost

5. You want nginx to serve static files from /var/www/html and forward API requests to an application server on port 4000. Which configuration correctly achieves this?

hard

A. location / { root /var/www/html; } location /api/ { proxy_pass http://localhost:4000/; }

B. location / { proxy_pass http://localhost:4000/; } location /api/ { root /var/www/html; }

C. location /api/ { root /var/www/html; } location / { proxy_pass http://localhost:4000/; }

D. location /api/ { proxy_pass http://localhost:4000/api/; } location / { root /var/www/html; }

Solution

1. Step 1: Assign root for static files

   The root directive in location / serves static files from /var/www/html.

2. Step 2: Forward API requests correctly

   The location /api/ block uses proxy_pass to forward API calls to the application server on port 4000.

3. Step 3: Verify order and correctness

   Static files served at root, API forwarded properly. Other options mix these roles incorrectly.

4. Final Answer:

   location / { root /var/www/html; } location /api/ { proxy_pass http://localhost:4000/; } -> Option A

5. Quick Check:

   Static files root + API proxy_pass = correct setup [OK]

Hint: Serve static at / root, proxy API at /api/ [OK]

Common Mistakes:

• Swapping root and proxy_pass locations
• Adding URI in proxy_pass causing path issues
• Not using trailing slash in location /api/