Concurrency and scaling in GCP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is concurrency in cloud computing?

Concurrency means handling many tasks or users at the same time without waiting for one to finish before starting another.

beginner

What does scaling mean in cloud services?

Scaling means changing the amount of resources (like servers or CPUs) to handle more or fewer users or tasks.

intermediate

What is the difference between vertical and horizontal scaling?

Vertical scaling adds more power (CPU, RAM) to one machine. Horizontal scaling adds more machines to share the work.

intermediate

How does Google Cloud Run handle concurrency?

Cloud Run lets multiple requests run at the same time in one container instance, improving resource use and speed.

beginner

Why is autoscaling important in cloud environments?

Autoscaling automatically adds or removes resources based on demand, saving money and keeping apps fast.

What does horizontal scaling involve?

A Adding more machines to share the workload

B Adding more CPU and RAM to one machine

C Reducing the number of users

D Stopping some services temporarily

Horizontal scaling means adding more machines to handle more work.

Which Google Cloud service automatically scales container instances based on traffic?

A BigQuery

B Cloud Storage

C Cloud Functions

D Cloud Run

Cloud Run automatically scales containers up or down depending on incoming requests.

What is concurrency best described as?

A Handling multiple tasks at the same time

B Adding more servers

C Stopping tasks to save resources

D Backing up data

Concurrency means doing many tasks simultaneously.

Why is autoscaling useful?

A It requires manual setup for each change

B It adjusts resources automatically to match demand

C It only works during business hours

D It reduces security risks

Autoscaling changes resources automatically to keep performance and save costs.

Vertical scaling means:

A Splitting tasks into smaller parts

B Adding more machines

C Adding more power to one machine

D Reducing the number of users

Vertical scaling means increasing CPU, RAM, or storage on a single machine.

Explain how concurrency and scaling work together in a cloud application.

Think about how many users can use an app at the same time and how the cloud adds resources.

Describe the difference between vertical and horizontal scaling with examples.

Imagine upgrading your computer vs buying more computers.

Practice

1. What does concurrency control in a Google Cloud service primarily manage?

easy

A. The network bandwidth available to the service

B. The total number of instances running

C. The number of requests one instance can handle at the same time

D. The amount of storage used by the service

Solution

1. Step 1: Understand concurrency meaning

   Concurrency means how many tasks or requests can happen at once in one place.

2. Step 2: Apply concurrency to cloud instances

   In cloud services, concurrency controls how many requests a single instance handles simultaneously.

3. Final Answer:

   The number of requests one instance can handle at the same time -> Option C

4. Quick Check:

   Concurrency = requests per instance [OK]

Hint: Concurrency = requests per instance at once [OK]

Common Mistakes:

• Confusing concurrency with total instances
• Thinking concurrency controls storage or bandwidth
• Mixing concurrency with scaling

2. Which of the following is the correct way to set maximum concurrency to 10 in a Google Cloud Run service using gcloud CLI?

easy

A. gcloud run services create SERVICE --max-concurrency=10

B. gcloud run services update SERVICE --concurrency=10

C. gcloud run services update SERVICE --max-instances=10

D. gcloud run services update SERVICE --concurrency-limit=10

Solution

1. Step 1: Identify correct flag for concurrency

   The correct flag to set concurrency in Cloud Run is --concurrency.

2. Step 2: Use update command for existing service

   To change concurrency, use 'gcloud run services update SERVICE --concurrency=10'.

3. Final Answer:

   gcloud run services update SERVICE --concurrency=10 -> Option B

4. Quick Check:

   Concurrency flag is --concurrency [OK]

Hint: Use --concurrency flag with update command [OK]

Common Mistakes:

• Using --max-concurrency which is invalid
• Confusing concurrency with max-instances
• Trying to set concurrency on service creation instead of update

3. Consider a Cloud Run service with max concurrency set to 5 and max instances set to 3. If 20 requests arrive simultaneously, how many instances will be used to handle the load?

medium

A. 5 instances

B. 4 instances

C. 20 instances

D. 3 instances

Solution

1. Step 1: Calculate needed instances for 20 requests with concurrency 5

   Each instance can handle 5 requests at once, so 20 requests need 20/5 = 4 instances.

2. Step 2: Apply max instances limit

   The max instances is set to 3, so the service cannot create more than 3 instances.

3. Final Answer:

   3 instances -> Option D

4. Quick Check:

   Max instances limit caps instance count [OK]

Hint: Max instances limit caps scaling even if more needed [OK]

Common Mistakes:

• Ignoring max instances limit and choosing 4
• Confusing concurrency with max instances
• Assuming one instance per request

4. You set concurrency to 80 on a Cloud Run service, but your app crashes under load. What is the most likely cause?

medium

A. The app cannot handle that many requests at once causing resource exhaustion

B. The max instances setting is too low

C. The service is not deployed in the right region

D. The concurrency setting must be at least 100

Solution

1. Step 1: Understand concurrency impact on app

   High concurrency means many requests handled simultaneously by one instance, increasing resource use.

2. Step 2: Link app crash to resource limits

   If the app crashes, it likely cannot handle that many requests at once, causing memory or CPU overload.

3. Final Answer:

   The app cannot handle that many requests at once causing resource exhaustion -> Option A

4. Quick Check:

   Too high concurrency can crash app [OK]

Hint: High concurrency can overload app resources [OK]

Common Mistakes:

• Blaming region instead of concurrency
• Assuming concurrency must be at least 100
• Ignoring app resource limits

5. You want your Cloud Run service to handle sudden traffic spikes efficiently without wasting resources during low traffic. Which combination of settings is best?

hard

A. Set concurrency to a moderate number (e.g., 10) and allow max instances to scale high

B. Set concurrency to 1 and max instances to 1

C. Set concurrency very high (e.g., 100) and max instances low (e.g., 2)

D. Disable concurrency and fix max instances to 10

Solution

1. Step 1: Balance concurrency and scaling for efficiency

   Moderate concurrency lets each instance handle multiple requests, saving resources.

2. Step 2: Allow max instances to scale high for spikes

   High max instances lets the service add instances when traffic spikes, keeping performance.

3. Final Answer:

   Set concurrency to a moderate number (e.g., 10) and allow max instances to scale high -> Option A

4. Quick Check:

   Moderate concurrency + high max instances = efficient scaling [OK]

Hint: Moderate concurrency + high max instances for spikes [OK]

Common Mistakes:

• Setting concurrency too low wastes instances
• Setting concurrency too high risks crashes
• Fixing max instances limits scaling