Backend services and backend buckets in GCP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a backend service in Google Cloud Platform?

A backend service is a configuration that defines how Cloud Load Balancing distributes traffic to backend instances or endpoints. It controls health checks, session affinity, and load balancing policies.

beginner

What is a backend bucket in Google Cloud Platform?

A backend bucket is a Cloud Storage bucket configured as a backend for Cloud Load Balancing. It serves static content directly to users through the load balancer.

intermediate

How does a backend service differ from a backend bucket?

A backend service routes traffic to compute resources like VM instances or instance groups, while a backend bucket serves static content from a Cloud Storage bucket.

beginner

Why are health checks important for backend services?

Health checks monitor the status of backend instances to ensure traffic is only sent to healthy, responsive resources, improving reliability and user experience.

intermediate

Can a backend bucket be used with HTTPS load balancing?

Yes, backend buckets can be used with HTTPS load balancers to serve static content securely over HTTPS.

What type of content does a backend bucket serve?

A Static content from Cloud Storage

B Dynamic content from VM instances

C Database queries

D API requests

Backend buckets serve static content stored in Cloud Storage buckets.

Which component controls traffic distribution in a backend service?

A Firewall rules

B Health checks

C Cloud Storage bucket

D Load balancing policies

Load balancing policies in backend services control how traffic is distributed to backends.

What ensures that traffic is only sent to healthy backend instances?

A Backend bucket

B Health checks

C Cloud DNS

D IAM roles

Health checks monitor backend instance health and prevent traffic to unhealthy instances.

Can backend services include instance groups as backends?

A Yes

B No

C Only for backend buckets

D Only for Cloud Storage

Backend services can include instance groups as backends to distribute traffic.

Which Google Cloud product is used to store content served by backend buckets?

A Compute Engine

B Cloud SQL

C Cloud Storage

D Cloud Functions

Backend buckets serve content stored in Cloud Storage.

Explain the roles of backend services and backend buckets in Google Cloud Load Balancing.

Think about how dynamic and static content are handled differently.

Describe how health checks improve the reliability of backend services.

Consider what happens if a backend instance stops responding.

Practice

1. What is the main purpose of a backend service in Google Cloud Load Balancing?

easy

A. To manage user authentication and authorization

B. To connect the load balancer to server groups for dynamic content

C. To monitor network traffic between regions

D. To store static files like images and videos

Solution

1. Step 1: Understand backend service role

   A backend service connects the load balancer to server groups that handle dynamic content like web apps.

2. Step 2: Differentiate from backend bucket

   Backend buckets connect to Cloud Storage for static content, not dynamic server groups.

3. Final Answer:

   To connect the load balancer to server groups for dynamic content -> Option B

4. Quick Check:

   Backend service = dynamic content connection [OK]

Hint: Backend service = dynamic servers, backend bucket = static storage [OK]

Common Mistakes:

• Confusing backend service with backend bucket
• Thinking backend service stores static files
• Assuming backend service manages authentication

2. Which of the following is the correct way to specify a backend bucket in a Google Cloud Load Balancer configuration?

easy

A. "backendService": "projects/my-project/global/backendBuckets/my-bucket"

B. "backendService": "projects/my-project/global/backendServices/my-service"

C. "backendBucket": "projects/my-project/global/backendServices/my-service"

D. "backendBucket": "projects/my-project/global/backendBuckets/my-bucket"

Solution

1. Step 1: Identify correct field for backend bucket

   The field to specify a backend bucket is "backendBucket" with the bucket's full path.

2. Step 2: Verify resource path matches backend bucket

   The resource path must include "backendBuckets" for a bucket, not "backendServices".

3. Final Answer:

   "backendBucket": "projects/my-project/global/backendBuckets/my-bucket" -> Option D

4. Quick Check:

   backendBucket field + backendBuckets path = correct [OK]

Hint: backendBucket key + backendBuckets path = backend bucket config [OK]

Common Mistakes:

• Using backendService key for backend bucket
• Mixing backendServices and backendBuckets in path
• Incorrect resource path format

3. Given this backend service configuration snippet, what will happen if the health check fails for all instances in the backend?

{
  "name": "my-backend-service",
  "healthChecks": ["projects/my-project/global/healthChecks/my-check"],
  "backends": [{"group": "projects/my-project/zones/us-central1-a/instanceGroups/my-group"}]
}

medium

A. The load balancer will stop sending traffic to this backend service

B. The load balancer will continue sending traffic to the backend service regardless

C. The load balancer will delete the backend service automatically

D. The load balancer will redirect traffic to the backend bucket

Solution

1. Step 1: Understand health check role

   Health checks monitor backend instances. If all fail, the backend is unhealthy.

2. Step 2: Effect on load balancer traffic

   Load balancer stops sending traffic to unhealthy backends to avoid errors.

3. Final Answer:

   The load balancer will stop sending traffic to this backend service -> Option A

4. Quick Check:

   Health check fail = no traffic sent [OK]

Hint: Failed health checks stop traffic to backend service [OK]

Common Mistakes:

• Assuming traffic continues despite health check failure
• Thinking backend service is deleted automatically
• Confusing backend service with backend bucket behavior

4. You configured a backend bucket for your load balancer but users report 403 errors when accessing static content. What is the most likely cause?

medium

A. The load balancer is not attached to any instance group

B. The backend service health check is failing

C. The backend bucket is missing the correct Cloud Storage permissions

D. The backend bucket name is misspelled in the load balancer config

Solution

1. Step 1: Check backend bucket access

   Backend buckets serve static content from Cloud Storage, which requires proper permissions.

2. Step 2: Identify cause of 403 errors

   Missing or incorrect permissions cause 403 errors because content cannot be accessed.

3. Final Answer:

   The backend bucket is missing the correct Cloud Storage permissions -> Option C

4. Quick Check:

   Missing permissions cause 403 on static content [OK]

Hint: 403 on static content usually means permission issues [OK]

Common Mistakes:

• Confusing backend bucket with backend service health checks
• Assuming instance groups affect backend buckets
• Overlooking spelling errors as cause

5. You want to serve a website with both dynamic content from Compute Engine instances and static content from Cloud Storage using a single HTTP(S) load balancer. How should you configure the backend services and backend buckets?

hard

A. Create a backend service for the instance group and a backend bucket for the Cloud Storage bucket, then configure URL map to route requests accordingly

B. Create only a backend bucket and upload dynamic content to Cloud Storage

C. Create multiple backend services for both static and dynamic content and ignore backend buckets

D. Use a backend service for static content and a backend bucket for dynamic content

Solution

1. Step 1: Understand content types and backends

   Dynamic content requires backend services connected to instance groups; static content uses backend buckets linked to Cloud Storage.

2. Step 2: Configure URL map routing

   Use URL map rules to route requests to backend service or backend bucket based on URL paths.

3. Final Answer:

   Create a backend service for the instance group and a backend bucket for the Cloud Storage bucket, then configure URL map to route requests accordingly -> Option A

4. Quick Check:

   Dynamic = backend service, static = backend bucket, route with URL map [OK]

Hint: Use URL map to route dynamic to backend service, static to backend bucket [OK]

Common Mistakes:

• Trying to serve dynamic content from backend bucket
• Ignoring URL map routing configuration
• Using backend service for static content