URL maps for routing in GCP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

How does a URL map route traffic based on host rules?

Consider a URL map configured with two host rules: one for example.com routing to backend service A, and another for test.com routing to backend service B. What happens when a request is sent to example.com?

A The request is rejected because only test.com is configured in the URL map.

B The request is routed to backend service B because test.com is the default host.

C The request is routed to a random backend service because host rules do not affect routing.

D The request is routed to backend service A because the host matches example.com.

💡 Hint

Think about how host rules match the domain name in the request.

URL maps use host rules to match the domain name in the incoming request. If the host matches example.com, the request is routed to the backend service assigned to that host rule.

❓ Configuration

intermediate

What is the effect of path matchers in a URL map?

A URL map has a path matcher that routes requests with path /images/* to backend service Images, and all other paths to backend service Default. What backend service handles a request to /images/logo.png?

A Backend service Default, because /images/logo.png is not an exact match.

B Backend service Images, but only if the host matches a specific host rule.

C Backend service Images, because the path matches /images/*.

D The request is rejected because no exact path match exists.

💡 Hint

Consider how path matchers use wildcard patterns.

Path matchers use wildcard patterns to match request paths. The pattern /images/* matches any path starting with /images/, so /images/logo.png matches and routes to backend service Images.

❓ Architecture

advanced

How to design a URL map for multi-region backend routing?

You want to route users to backend services in different regions based on URL path prefixes: /us/* to US backend, /eu/* to EU backend, and all others to a global backend. Which URL map configuration achieves this?

A Create separate URL maps for each region and use DNS to route users.

B Create path matchers for /us/* routing to US backend, /eu/* routing to EU backend, and a default path matcher routing to global backend.

C Use host rules to route /us/* and /eu/* paths to respective backends.

D Configure backend services to detect user location and redirect requests.

💡 Hint

Think about how path matchers can route based on URL paths.

URL maps can use path matchers with wildcard paths to route requests to different backends based on URL prefixes. This allows routing /us/* to US backend, /eu/* to EU backend, and all others to a global backend.

❓ security

advanced

What happens if a URL map has no default backend service configured?

A URL map is created with host and path rules but no default backend service. What is the expected behavior when a request does not match any host or path rule?

A The request is rejected with a 404 Not Found error.

B The request is routed to the first backend service defined in the URL map.

C The request is routed to a global default backend service automatically.

D The request is redirected to the root path of the first host rule.

💡 Hint

Consider what happens when no matching rule exists and no default is set.

If no default backend service is configured, and the request does not match any host or path rule, the load balancer returns a 404 Not Found error because it does not know where to send the request.

✅ Best Practice

expert

How to optimize URL map configuration for minimal latency in global load balancing?

You manage a global HTTP(S) load balancer with multiple backend services worldwide. Which URL map design best reduces latency for users worldwide?

A Use host and path rules to route requests to backend services closest to the user's region, combined with Cloud CDN for caching.

B Route all requests to a single global backend service to simplify configuration.

C Use only host rules without path matchers to reduce URL map complexity.

D Configure URL maps to route based on IP address ranges instead of URL paths.

💡 Hint

Think about combining routing and caching to improve latency.

Routing users to the nearest backend service using host and path rules reduces latency. Adding Cloud CDN caches content closer to users, further improving response times.

Practice

1. What is the main purpose of a URL map in Google Cloud Platform's load balancing?

easy

A. To store user data for web applications

B. To create virtual machines automatically

C. To route incoming web traffic to different backend services based on URL paths or hosts

D. To monitor network traffic usage

Solution

1. Step 1: Understand URL map role

   A URL map directs web traffic to backend services depending on URL patterns.

2. Step 2: Identify correct function

   Routing based on URL paths or hosts matches the description of URL maps.

3. Final Answer:

   To route incoming web traffic to different backend services based on URL paths or hosts -> Option C

4. Quick Check:

   URL maps route traffic = B [OK]

Hint: URL maps decide backend by URL pattern [OK]

Common Mistakes:

• Confusing URL maps with storage or VM services
• Thinking URL maps monitor traffic instead of routing
• Assuming URL maps create resources automatically

2. Which of the following is the correct syntax to define a path matcher in a GCP URL map configuration?

easy

A. "pathMatcher": {"name": "pm1", "defaultService": "backend1"}

B. "pathMatchers": [{"name": "pm1", "defaultService": "backend1"}]

C. "pathMatchers": {"name": "pm1", "defaultService": "backend1"}

D. "pathMatcher": [{"name": "pm1", "defaultService": "backend1"}]

Solution

1. Step 1: Identify correct key for multiple path matchers

   The key for multiple path matchers is plural: "pathMatchers" with an array value.

2. Step 2: Confirm value type

   The value must be an array of objects, so square brackets [] are needed.

3. Final Answer:

   "pathMatchers": [{"name": "pm1", "defaultService": "backend1"}] -> Option B

4. Quick Check:

   Multiple path matchers use "pathMatchers" array = A [OK]

Hint: Use plural "pathMatchers" with array brackets [OK]

Common Mistakes:

• Using singular "pathMatcher" for multiple entries
• Using object instead of array for pathMatchers
• Mixing singular/plural keys incorrectly

3. Given this URL map snippet, which backend service will handle the request to https://example.com/images/logo.png?

{
  "defaultService": "backend-default",
  "pathMatchers": [
    {
      "name": "pm-images",
      "defaultService": "backend-images",
      "pathRules": [
        {"paths": ["/images/*"], "service": "backend-images"}
      ]
    }
  ]
}

medium

A. backend-images

B. No backend matches, request fails

C. backend-logo

D. backend-default

Solution

1. Step 1: Check path rules for "/images/*"

   The path matcher "pm-images" has a path rule matching "/images/*" directing to "backend-images".

2. Step 2: Match request URL path

   The request path "/images/logo.png" matches the "/images/*" pattern, so it routes to "backend-images".

3. Final Answer:

   backend-images -> Option A

4. Quick Check:

   Path "/images/*" matches request = backend-images [OK]

Hint: Match URL path to pathRules first, else defaultService [OK]

Common Mistakes:

• Choosing defaultService without checking pathRules
• Assuming no match causes failure instead of default routing
• Confusing path patterns with exact matches

4. You have this URL map configuration snippet:

{
  "defaultService": "backend-default",
  "pathMatchers": [
    {
      "name": "pm1",
      "defaultService": "backend1",
      "pathRules": [
        {"paths": ["/app/*"], "service": "backend-app"}
      ]
    }
  ]
}

Why does a request to https://example.com/app go to backend-default instead of backend-app?

medium

A. The defaultService overrides all pathRules

B. The path matcher name "pm1" is invalid

C. The backend service "backend-app" is not defined

D. The path "/app" does not match the pattern "/app/*" which requires a trailing slash

Solution

1. Step 1: Understand path pattern matching

   The pattern "/app/*" matches paths starting with "/app/" but not "/app" exactly.

2. Step 2: Check request path against pattern

   The request path "/app" lacks the trailing slash, so it does not match "/app/*" and falls back to defaultService.

3. Final Answer:

   The path "/app" does not match the pattern "/app/*" which requires a trailing slash -> Option D

4. Quick Check:

   Trailing slash matters in path patterns = C [OK]

Hint: Path patterns with * need trailing slash to match [OK]

Common Mistakes:

• Assuming "/app" matches "/app/*" without slash
• Thinking defaultService always overrides pathRules
• Believing backend service must be explicitly defined to route

5. You want to route requests to https://example.com/api/v1/users to backend-v1 and requests to https://example.com/api/v2/users to backend-v2. Which URL map configuration correctly achieves this?

hard

A. {
"defaultService": "backend-default",
"pathMatchers": [
{
"name": "pm-api",
"defaultService": "backend-default",
"pathRules": [
{"paths": ["/api/v1/*"], "service": "backend-v1"},
{"paths": ["/api/v2/*"], "service": "backend-v2"}
]
}
]
}

B. {
"defaultService": "backend-default",
"pathMatchers": [
{
"name": "pm-api",
"defaultService": "backend-v1",
"pathRules": [
{"paths": ["/api/v1/*"], "service": "backend-v1"},
{"paths": ["/api/v2/*"], "service": "backend-v2"}
]
}
]
}

C. {
"defaultService": "backend-default",
"pathMatchers": [
{
"name": "pm-api",
"defaultService": "backend-v2",
"pathRules": [
{"paths": ["/api/v1/*"], "service": "backend-v1"}
]
}
]
}

D. {
"defaultService": "backend-default",
"pathMatchers": [
{
"name": "pm-api",
"defaultService": "backend-default",
"pathRules": [
{"paths": ["/api/*"], "service": "backend-v1"},
{"paths": ["/api/*"], "service": "backend-v2"}
]
}
]
}

Solution

1. Step 1: Check path rules for specific version routing

   { "defaultService": "backend-default", "pathMatchers": [ { "name": "pm-api", "defaultService": "backend-default", "pathRules": [ {"paths": ["/api/v1/*"], "service": "backend-v1"}, {"paths": ["/api/v2/*"], "service": "backend-v2"} ] } ] } defines two distinct path rules: "/api/v1/*" to "backend-v1" and "/api/v2/*" to "backend-v2" which matches requirements.

2. Step 2: Verify defaultService and pathRules consistency

   { "defaultService": "backend-default", "pathMatchers": [ { "name": "pm-api", "defaultService": "backend-default", "pathRules": [ {"paths": ["/api/v1/*"], "service": "backend-v1"}, {"paths": ["/api/v2/*"], "service": "backend-v2"} ] } ] } uses "backend-default" as defaultService, so unmatched paths go there, which is correct.

3. Step 3: Identify issues in other options

   { "defaultService": "backend-default", "pathMatchers": [ { "name": "pm-api", "defaultService": "backend-v1", "pathRules": [ {"paths": ["/api/v1/*"], "service": "backend-v1"}, {"paths": ["/api/v2/*"], "service": "backend-v2"} ] } ] } sets defaultService to "backend-v1" which may misroute unmatched paths. { "defaultService": "backend-default", "pathMatchers": [ { "name": "pm-api", "defaultService": "backend-v2", "pathRules": [ {"paths": ["/api/v1/*"], "service": "backend-v1"} ] } ] } misses "/api/v2/*" pathRule. { "defaultService": "backend-default", "pathMatchers": [ { "name": "pm-api", "defaultService": "backend-default", "pathRules": [ {"paths": ["/api/*"], "service": "backend-v1"}, {"paths": ["/api/*"], "service": "backend-v2"} ] } ] } duplicates "/api/*" paths causing conflict.

4. Final Answer:

   Option A correctly routes /api/v1/* and /api/v2/* to respective backends -> Option A

5. Quick Check:

   Distinct pathRules for versions = A [OK]

Hint: Use distinct pathRules for each version prefix [OK]

Common Mistakes:

• Setting defaultService to one version backend
• Missing pathRule for one version
• Duplicating same path pattern causing conflicts