Cloud CDN integration in GCP - Step-by-Step Execution

Process Flow - Cloud CDN integration

Create Backend Service

↓

Enable Cloud CDN on Backend

↓

Create URL Map

↓

Create Target HTTP(S) Proxy

↓

Create Global Forwarding Rule

↓

Client Requests -> CDN Cache

↓

Cache Hit?

Yes→Serve from Cache

No↓

Fetch from Backend

↓

Cache Response

↓

Serve to Client

This flow shows how to set up Cloud CDN with a backend service and how client requests are served from cache or backend.

Execution Sample

GCP

gcloud compute backend-services create my-backend \
  --protocol HTTP --port-name http --global

gcloud compute backend-services update my-backend \
  --enable-cdn --global

gcloud compute url-maps create my-map \
  --default-service my-backend

gcloud compute target-http-proxies create my-proxy \
  --url-map my-map

gcloud compute forwarding-rules create my-rule \
  --global --target-http-proxy my-proxy --ports 80

This code creates a backend service, enables Cloud CDN, sets up URL map, proxy, and forwarding rule to serve cached content globally.

Process Table

Step	Action	Resource Created/Updated	Effect	Next Step
1	Create backend service	Backend Service 'my-backend'	Backend ready to serve HTTP	Enable CDN on backend
2	Enable CDN	Backend Service 'my-backend'	CDN caching enabled	Create URL map
3	Create URL map	URL Map 'my-map'	Routes requests to backend	Create target HTTP proxy
4	Create target HTTP proxy	Target HTTP Proxy 'my-proxy'	Handles HTTP requests	Create forwarding rule
5	Create global forwarding rule	Forwarding Rule 'my-rule'	Listens on port 80 globally	Ready to serve requests
6	Client sends request	Request received	Check cache for content	Cache hit?
7	Cache hit	Serve cached content	Fast response from CDN	End
8	Cache miss	Fetch from backend	Backend serves content	Cache response and serve
9	Cache response	Content cached	Future requests faster	Serve to client
10	Serve to client	Response sent	Client receives content	End

💡 Execution stops after serving client content either from cache or backend.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	After Step 7/8	After Step 9	Final
Backend Service	None	Created	CDN Enabled	CDN Enabled	CDN Enabled	CDN Enabled	CDN Enabled	CDN Enabled	CDN Enabled	CDN Enabled
URL Map	None	None	None	Created	Created	Created	Created	Created	Created	Created
Target HTTP Proxy	None	None	None	None	Created	Created	Created	Created	Created	Created
Forwarding Rule	None	None	None	None	None	Created	Created	Created	Created	Created
Cache Status	Empty	Empty	Empty	Empty	Empty	Empty	Check Cache	Hit or Miss	Updated if Miss	Hit or Miss
Client Response	None	None	None	None	None	None	Waiting	From Cache or Backend	From Cache or Backend	Sent

Key Moments - 3 Insights

Why do we enable CDN after creating the backend service and not before?

Because the backend service must exist first to enable CDN on it. See execution_table rows 1 and 2 where backend is created first, then CDN is enabled.

What happens when a client request results in a cache miss?

The request goes to the backend service to fetch content, which is then cached for future requests. This is shown in execution_table rows 8 and 9.

Why do we need a URL map and target HTTP proxy in this setup?

The URL map directs requests to the backend service, and the target HTTP proxy handles incoming HTTP requests globally. This routing setup is essential before creating the forwarding rule (rows 3 and 4).

Visual Quiz - 3 Questions

Look at the execution_table, at which step is Cloud CDN enabled on the backend service?

A Step 1

B Step 2

C Step 3

D Step 5

💡 Hint

Check the 'Action' and 'Effect' columns in execution_table row 2.

According to variable_tracker, what is the cache status after step 7?

A Empty

B Check Cache

C Hit or Miss

D Updated if Miss

💡 Hint

Look at the 'Cache Status' row and the column 'After Step 7/8' in variable_tracker.

If the forwarding rule was not created, what would be the impact on serving client requests?

A Requests would still be served from cache

B Requests would be routed directly to backend without caching

C Requests would not reach the proxy and fail

D Requests would be served from a different region

💡 Hint

Refer to execution_table row 5 and the role of forwarding rules in routing.

Concept Snapshot

Cloud CDN integration steps:
1. Create backend service.
2. Enable CDN on backend.
3. Create URL map to route requests.
4. Create target HTTP proxy.
5. Create global forwarding rule.
Client requests hit CDN cache first; cache miss fetches from backend.

Full Transcript

This visual execution trace shows how to integrate Cloud CDN with a backend service on Google Cloud Platform. First, a backend service is created to serve HTTP traffic. Then, Cloud CDN is enabled on this backend to cache content globally. A URL map is created to route incoming requests to the backend service. Next, a target HTTP proxy is set up to handle HTTP requests using the URL map. A global forwarding rule listens on port 80 and directs client requests to the proxy. When a client sends a request, the CDN cache is checked. If the content is cached (cache hit), it is served immediately, providing fast response. If not cached (cache miss), the request goes to the backend service, which serves the content and caches it for future requests. This setup improves performance by serving content closer to users worldwide. Variables like backend service status, URL map, proxy, forwarding rule, cache status, and client response change step-by-step as the setup progresses and requests are handled.

Practice

1. What is the primary purpose of Google Cloud CDN in a web application architecture?

easy

A. To cache content closer to users for faster delivery

B. To store user data securely in the cloud

C. To manage database connections efficiently

D. To provide virtual machines for computation

Solution

1. Step 1: Understand Cloud CDN's role

   Cloud CDN caches static and dynamic content at edge locations near users to reduce latency.

2. Step 2: Compare with other options

   Options A, B, and D describe other cloud services unrelated to CDN's caching function.

3. Final Answer:

   To cache content closer to users for faster delivery -> Option A

4. Quick Check:

   Cloud CDN = caching content near users [OK]

Hint: Cloud CDN speeds up content by caching near users [OK]

Common Mistakes:

• Confusing CDN with storage or compute services
• Thinking CDN manages databases
• Assuming CDN is for security only

2. Which GCP component must be configured to enable Cloud CDN for a backend service?

easy

A. Create a Cloud Storage bucket

B. Set up a Cloud SQL instance

C. Enable CDN on the backend service

D. Configure a Pub/Sub topic

Solution

1. Step 1: Identify CDN enabling step

   Cloud CDN is enabled by turning on the CDN option on the backend service linked to the load balancer.

2. Step 2: Eliminate unrelated components

   Cloud Storage buckets, Cloud SQL, and Pub/Sub are unrelated to enabling CDN on backend services.

3. Final Answer:

   Enable CDN on the backend service -> Option C

4. Quick Check:

   Enable CDN = backend service setting [OK]

Hint: Enable CDN directly on backend service in GCP [OK]

Common Mistakes:

• Trying to enable CDN on storage buckets only
• Confusing CDN with database or messaging setup
• Missing the backend service step

3. Given this simplified request flow for Cloud CDN: User -> HTTP(S) Load Balancer -> Backend Service (CDN enabled) -> Origin Server. What happens when a user requests a cached object that is still valid in the CDN cache?

medium

A. The load balancer fetches the object from the origin server

B. The CDN serves the cached object directly to the user

C. The backend service disables caching for that request

D. The request is redirected to another region

Solution

1. Step 1: Understand CDN cache hit behavior

   If the requested object is cached and valid, Cloud CDN serves it directly from the cache without contacting the origin.

2. Step 2: Analyze other options

   The load balancer fetches the object from the origin server is incorrect because the origin is bypassed on cache hit; options B and C do not describe CDN cache behavior.

3. Final Answer:

   The CDN serves the cached object directly to the user -> Option B

4. Quick Check:

   Cache hit = CDN serves cached content [OK]

Hint: Cache hit means CDN serves content, no origin call [OK]

Common Mistakes:

• Assuming origin is always contacted
• Confusing backend service disabling cache
• Thinking request redirects on cache hit

4. You configured Cloud CDN but notice that content is not being cached. Which of the following is the most likely misconfiguration?

medium

A. CDN is not enabled on the backend service

B. The load balancer is using HTTP instead of HTTPS

C. The origin server is unreachable

D. The forwarding rule is missing a static IP

Solution

1. Step 1: Check CDN enablement

   Cloud CDN must be explicitly enabled on the backend service to cache content.

2. Step 2: Evaluate other options

   Using HTTP vs HTTPS or missing static IP does not prevent caching; origin unreachable causes errors but not silent no-cache.

3. Final Answer:

   CDN is not enabled on the backend service -> Option A

4. Quick Check:

   CDN enabled on backend = caching works [OK]

Hint: Always enable CDN on backend service to cache content [OK]

Common Mistakes:

• Assuming HTTPS is required for caching
• Thinking static IP affects caching
• Ignoring backend service CDN setting

5. You want to design a scalable web app using Cloud CDN to serve static assets from a Cloud Storage bucket. Which setup correctly integrates Cloud CDN for this use case?

hard

A. Configure a forwarding rule to Cloud Storage and enable CDN there

B. Directly enable CDN on the Cloud Storage bucket without a load balancer

C. Use Cloud SQL as backend and enable CDN on it

D. Create a backend bucket pointing to Cloud Storage, enable CDN on it, then configure an HTTP(S) load balancer with this backend bucket

Solution

1. Step 1: Understand Cloud CDN integration with storage

   Cloud CDN integrates with Cloud Storage via a backend bucket configured in an HTTP(S) load balancer.

2. Step 2: Evaluate options

   Directly enable CDN on the Cloud Storage bucket without a load balancer is invalid because CDN cannot be enabled directly on storage buckets; C and D misuse services or configurations.

3. Final Answer:

   Create a backend bucket pointing to Cloud Storage, enable CDN on it, then configure an HTTP(S) load balancer with this backend bucket -> Option D

4. Quick Check:

   Backend bucket + load balancer + CDN = correct setup [OK]

Hint: Use backend bucket with load balancer to enable CDN on storage [OK]

Common Mistakes:

• Trying to enable CDN directly on storage buckets
• Using databases as backend for CDN
• Misconfiguring forwarding rules without load balancer