Service account keys management in GCP - Time & Space Complexity

Time Complexity: Service account keys management

O(n)

Understanding Time Complexity

When managing service account keys, it's important to understand how the number of keys affects the time it takes to list, create, or delete them.

We want to know how the work grows as we handle more keys.

Scenario Under Consideration

Analyze the time complexity of the following operation sequence.

// List all keys for a service account
keys = iam.projects.serviceAccounts.keys.list({
  name: 'projects/-/serviceAccounts/service-account-email'
})

// Delete each key one by one
for (const key of keys.keys) {
  iam.projects.serviceAccounts.keys.delete({
    name: key.name
  })
}

// Create a new key
newKey = iam.projects.serviceAccounts.keys.create({
  name: 'projects/-/serviceAccounts/service-account-email'
})

This sequence lists all keys, deletes them one by one, then creates a new key for a service account.

Identify Repeating Operations

Identify the API calls, resource provisioning, data transfers that repeat.

• Primary operation: Deleting each service account key individually.
• How many times: Once per existing key, so the number grows with the number of keys.

How Execution Grows With Input

As the number of keys increases, the number of delete calls grows directly with it.

Input Size (n)	Approx. Api Calls/Operations
10	List (1) + Delete (10) + Create (1) = 12
100	List (1) + Delete (100) + Create (1) = 102
1000	List (1) + Delete (1000) + Create (1) = 1002

Pattern observation: The total operations increase roughly in direct proportion to the number of keys.

Final Time Complexity

Time Complexity: O(n)

This means the time to manage keys grows linearly with the number of keys you have.

Common Mistake

[X] Wrong: "Deleting all keys happens in one single API call regardless of how many keys exist."

[OK] Correct: Each key must be deleted individually, so the number of delete calls grows with the number of keys.

Interview Connect

Understanding how operations scale with resource count shows you can plan and manage cloud resources efficiently, a key skill in real projects.

Self-Check

"What if we batch delete keys in groups instead of one by one? How would the time complexity change?"

Practice

1. What is the main purpose of a service account key in Google Cloud?

easy

A. To manage billing information for Google Cloud projects

B. To store user passwords for Google Cloud accounts

C. To allow programs to securely access Google Cloud resources

D. To create virtual machines automatically

Solution

1. Step 1: Understand service account keys

   Service account keys are used by programs, not humans, to access Google Cloud securely.

2. Step 2: Identify the correct purpose

   They provide credentials for applications to authenticate and interact with cloud services.

3. Final Answer:

   To allow programs to securely access Google Cloud resources -> Option C

4. Quick Check:

   Service account keys = secure program access [OK]

Hint: Keys let programs access cloud securely, not users [OK]

Common Mistakes:

• Confusing keys with user passwords
• Thinking keys manage billing
• Believing keys create virtual machines

2. Which gcloud command correctly creates a new service account key for the account [e-mail]?

easy

A. gcloud iam service-accounts keys create key.json --iam-account=[e-mail]

B. gcloud iam service-accounts create key.json --account=[e-mail]

C. gcloud service-accounts keys create key.json --account=[e-mail]

D. gcloud iam keys create key.json --iam-account=[e-mail]

Solution

1. Step 1: Identify correct gcloud command syntax

   The correct command to create a key is gcloud iam service-accounts keys create with the --iam-account flag.

2. Step 2: Match the command with the options

   gcloud iam service-accounts keys create key.json --iam-account=[e-mail] matches the correct syntax exactly.

3. Final Answer:

   gcloud iam service-accounts keys create key.json --iam-account=[e-mail] -> Option A

4. Quick Check:

   Correct command syntax = gcloud iam service-accounts keys create key.json --iam-account=[e-mail] [OK]

Hint: Use 'iam service-accounts keys create' with --iam-account [OK]

Common Mistakes:

• Using 'create' without 'keys'
• Wrong flag like --account instead of --iam-account
• Omitting 'iam' in the command

3. What will be the output of the following command?

gcloud iam service-accounts keys list --iam-account=[e-mail]

Assuming there are two active keys for this service account.

medium

A. A prompt to create a new key

B. An error saying no keys found

C. A list of all service accounts in the project

D. A list showing details of the two active keys including key IDs and creation dates

Solution

1. Step 1: Understand the command purpose

   The command lists keys for the specified service account.

2. Step 2: Interpret expected output

   Since two active keys exist, the output will show their details like key IDs and creation dates.

3. Final Answer:

   A list showing details of the two active keys including key IDs and creation dates -> Option D

4. Quick Check:

   Listing keys shows active keys details [OK]

Hint: List keys command shows active keys info [OK]

Common Mistakes:

• Expecting an error if keys exist
• Confusing keys list with service accounts list
• Thinking it prompts for key creation

4. You run the command:

gcloud iam service-accounts keys delete 123abc --iam-account=[e-mail]

But get an error saying the key ID does not exist. What is the most likely cause?

medium

A. The key ID is incorrect or does not belong to the specified service account

B. The service account email is misspelled

C. You need to create a new key before deleting

D. The project ID is missing from the command

Solution

1. Step 1: Analyze the error message

   The error says the key ID does not exist, meaning the key ID is invalid or not linked to the service account.

2. Step 2: Check command components

   The service account email may be correct, and project ID is not required here if default is set. Creating a key before deleting is unnecessary.

3. Final Answer:

   The key ID is incorrect or does not belong to the specified service account -> Option A

4. Quick Check:

   Invalid key ID causes deletion error [OK]

Hint: Check key ID matches service account keys [OK]

Common Mistakes:

• Assuming project ID is mandatory in this command
• Thinking you must create a key before deleting
• Ignoring key ID correctness

5. You want to rotate service account keys to improve security. Which sequence of actions is the best practice?

hard

A. Delete the old key first, then create a new key and update applications

B. Create a new key, update your applications to use it, then delete the old key

C. Create multiple keys and use them all simultaneously without deleting any

D. Keep using the old key until it expires, then create a new key

Solution

1. Step 1: Understand key rotation best practice

   To avoid downtime, first create a new key and update applications to use it.

2. Step 2: Remove old key after update

   Once applications use the new key, delete the old key to reduce risk.

3. Final Answer:

   Create a new key, update your applications to use it, then delete the old key -> Option B

4. Quick Check:

   New key first, then delete old key [OK]

Hint: Add new key before deleting old one to avoid downtime [OK]

Common Mistakes:

• Deleting old key before updating apps
• Using multiple keys unnecessarily
• Waiting for old key to expire before rotating