API routing with location blocks in Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a location block in nginx?

A location block defines how nginx should respond to requests for specific URL paths. It helps route requests to different parts of your server or backend services.

beginner

How do you route API requests starting with /api/ to a backend server in nginx?

Use a location /api/ { proxy_pass http://backend_server; } block to forward all requests starting with /api/ to the backend server.

beginner

What does the proxy_pass directive do inside a location block?

It tells nginx to forward the incoming request to another server or service, acting like a middleman between the client and backend.

intermediate

How can you match exact URLs versus URL prefixes in nginx location blocks?

Use = /exact/path for exact matches and /prefix/ for prefix matches. Exact matches take priority over prefix matches.

intermediate

Why is the order of location blocks important in nginx?

nginx chooses the best matching location block based on specific rules. Exact matches are checked first, then prefix matches. Order affects which block handles a request.

Which nginx directive forwards API requests to a backend server?

A proxy_pass

B listen

C server_name

D root

The proxy_pass directive forwards requests to another server.

How do you define a location block that matches all URLs starting with /api/?

A location = /api/ {}

B location ^~ /api/ {}

C location ~ /api/ {}

D location /api/ {}

A simple prefix match uses location /api/ {}.

What happens if you have both location = /api and location /api/ blocks?

A The exact match is used

B nginx throws an error

C The prefix match is used

D Both blocks run

Exact matches take priority over prefix matches.

Which directive specifies the port nginx listens on?

A server_name

B proxy_pass

C listen

D location

The listen directive sets the port for nginx.

If you want to route /api/users to a backend, which location block is best?

A location = /api/users {}

B location /api/ {}

C location / {}

D location ~ /users {}

The prefix match /api/ covers /api/users.

Explain how nginx uses location blocks to route API requests.

Think about how nginx decides which block handles a request.

Describe how to configure nginx to send all requests starting with /api/ to a backend server.

Focus on the location block and proxy_pass.

Practice

1. What does a location block in an nginx configuration do?

easy

A. Sets the maximum file upload size

B. Defines server IP addresses

C. Specifies the server's operating system

D. Routes incoming requests based on URL paths

Solution

1. Step 1: Understand the purpose of location blocks

   Location blocks in nginx are used to match parts of the URL path to decide how to handle requests.

2. Step 2: Identify what location blocks control

   They control routing of requests to different handlers or backends based on the URL.

3. Final Answer:

   Routes incoming requests based on URL paths -> Option D

4. Quick Check:

   Location blocks = URL routing [OK]

Hint: Location blocks match URL paths to route requests [OK]

Common Mistakes:

• Confusing location blocks with server IP settings
• Thinking location blocks set server OS
• Assuming location blocks control upload size

2. Which of the following is the correct syntax to define a location block that matches exactly the path /api/v1/users?

easy

A. location = /api/v1/users { ... }

B. location /api/v1/users { ... }

C. location ~ /api/v1/users { ... }

D. location ^~ /api/v1/users { ... }

Solution

1. Step 1: Recall nginx location modifiers

   The = modifier means exact match of the URL path.

2. Step 2: Match the exact path syntax

   Using location = /api/v1/users matches only that exact path.

3. Final Answer:

   location = /api/v1/users { ... } -> Option A

4. Quick Check:

   Exact match uses = modifier [OK]

Hint: Use '=' for exact path match in location [OK]

Common Mistakes:

• Using no modifier for exact match
• Using regex (~) when exact match needed
• Using ^~ which is prefix but not exact

3. Given this nginx config snippet:

location /api/ {
  proxy_pass http://backend-service/;
}

What happens when a client requests /api/users?

medium

A. Request is forwarded to http://backend-service/users

B. Request is forwarded to http://backend-service/api/users

C. Request is served locally from /api/users directory

D. Request returns 404 Not Found

Solution

1. Step 1: Understand proxy_pass with trailing slash

   When proxy_pass URL ends with a slash, nginx replaces the matching part of the request URI.

2. Step 2: Apply to the request path

   The matching prefix /api/ is replaced by / from proxy_pass, so /api/users becomes /users at backend.

3. Final Answer:

   Request is forwarded to http://backend-service/users -> Option A

4. Quick Check:

   proxy_pass with trailing slash replaces prefix [OK]

Hint: Trailing slash in proxy_pass replaces matched prefix [OK]

Common Mistakes:

• Assuming proxy_pass appends full original URI
• Confusing local serving with proxying
• Ignoring trailing slash effect in proxy_pass

4. Identify the error in this nginx location block:

location /api {
  proxy_pass http://backend-service/;
}

medium

A. Missing trailing slash in location path causes wrong proxying

B. location path should end with a slash to match subpaths

C. proxy_pass URL must not have a trailing slash

D. No error; configuration is correct

Solution

1. Step 1: Check location path matching behavior

   Without a trailing slash, location /api matches only the exact path /api and not subpaths like /api/users.

2. Step 2: Correct usage for subpath matching

   To match /api and all subpaths, use location /api/ with trailing slash.

3. Final Answer:

   location path should end with a slash to match subpaths -> Option B

4. Quick Check:

   Trailing slash in location matches subpaths [OK]

Hint: Add trailing slash in location to match subpaths [OK]

Common Mistakes:

• Thinking proxy_pass trailing slash is wrong here
• Assuming location without slash matches subpaths
• Believing config is error-free without checking path

5. You want to route all requests starting with /api/v2/ to http://v2-backend/ but requests exactly to /api/v2/status should return a static JSON response locally. Which nginx config achieves this?

hard

A. location /api/v2/status { return 200 '{"status":"ok"}'; }
location ^~ /api/v2/ { proxy_pass http://v2-backend/; }

B. location /api/v2/status { proxy_pass http://v2-backend/status; }
location /api/v2/ { proxy_pass http://v2-backend/; }

C. location = /api/v2/status { return 200 '{"status":"ok"}'; }
location /api/v2/ { proxy_pass http://v2-backend/; }

D. location /api/v2/ { proxy_pass http://v2-backend/; }
location = /api/v2/status { proxy_pass http://v2-backend/status; }

Solution

1. Step 1: Use exact match for static response

   Use location = /api/v2/status to match exactly that path and return static JSON.

2. Step 2: Use prefix match for all other /api/v2/ requests

   Use location /api/v2/ to proxy all other requests to backend.

3. Final Answer:

   location = /api/v2/status { return 200 '{"status":"ok"}'; } location /api/v2/ { proxy_pass http://v2-backend/; } -> Option C

4. Quick Check:

   Exact match first, then prefix proxy [OK]

Hint: Exact match location before prefix for special cases [OK]

Common Mistakes:

• Placing prefix location before exact match causing override
• Using proxy_pass for static JSON response
• Not escaping JSON properly in return directive