Data privacy and compliance (GDPR) in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding GDPR Data Subject Rights

Which of the following is NOT a right granted to data subjects under GDPR?

A Right to demand unlimited data sharing with third parties

B Right to have personal data erased (right to be forgotten)

C Right to access personal data held by an organization

D Right to data portability to another service provider

💡 Hint

Think about what GDPR protects regarding personal data sharing.

GDPR does not grant the right to demand unlimited data sharing with third parties. Instead, it controls and restricts data sharing to protect privacy.

❓ Architecture

intermediate

Designing a GDPR-Compliant Data Deletion Flow

You need to design a system flow for handling user requests to delete their personal data under GDPR. Which step should NOT be part of the flow?

A Immediately delete all data without any backup or logs

B Log the deletion request and action for audit purposes

C Verify the identity of the requester before processing deletion

D Notify the user once deletion is complete

💡 Hint

Consider GDPR requirements for accountability and audit trails.

GDPR requires organizations to keep records of processing activities, including deletions, for accountability. Immediate deletion without logs breaks this rule.

❓ scaling

advanced

Scaling Data Access Requests in a Multi-Region System

Your global service receives thousands of GDPR data access requests daily from users in different regions. Which architectural approach best supports scalable, compliant handling of these requests?

A Centralize all personal data in one region and process all requests there

B Process requests manually via email to ensure accuracy

C Ignore regional data residency and process requests in any data center

D Distribute data regionally and process requests locally with synchronized audit logs

💡 Hint

Think about data residency laws and system scalability.

Distributing data regionally respects data residency laws and processing requests locally reduces latency and scales better. Synchronizing audit logs ensures compliance.

❓ tradeoff

advanced

Tradeoffs in Data Encryption for GDPR Compliance

When implementing encryption for personal data to comply with GDPR, which tradeoff is most important to consider?

A Not encrypting data to improve system performance

B Encrypting all data at rest and in transit may increase latency and cost

C Encrypting only non-personal data to save resources

D Using weak encryption algorithms to reduce complexity

💡 Hint

GDPR requires protection of personal data but also consider system impact.

Encrypting all personal data protects privacy but may increase latency and cost. Balancing security and performance is key.

❓ estimation

expert

Estimating Storage Needs for GDPR Data Retention

Your system stores personal data for 5 years to comply with GDPR retention policies. If you have 1 million users, each generating 10 KB of personal data monthly, estimate the total storage needed for personal data retention.

A 50 TB

B 5 TB

C 600 GB

D 600 TB

💡 Hint

Calculate monthly data per user, multiply by users and months in 5 years, then convert to TB.

Per month: 1,000,000 users × 10 KB = 10,000,000 KB ≈ 10 GB
Over 60 months: 10 GB × 60 = 600 GB

Practice

1. What is the main purpose of GDPR in system design?

easy

A. To reduce server costs by deleting all user data immediately

B. To protect user privacy and ensure data is handled responsibly

C. To allow unlimited data collection for marketing

D. To increase system performance by caching user data

Solution

1. Step 1: Understand GDPR's goal

   GDPR aims to protect personal data and privacy of users in the EU.

2. Step 2: Match purpose to options

   Only To protect user privacy and ensure data is handled responsibly mentions protecting privacy and responsible data handling, which aligns with GDPR.

3. Final Answer:

   To protect user privacy and ensure data is handled responsibly -> Option B

4. Quick Check:

   GDPR = Protect privacy [OK]

Hint: GDPR = user privacy protection [OK]

Common Mistakes:

• Confusing GDPR with performance or cost goals
• Thinking GDPR allows unlimited data collection
• Ignoring privacy as the core focus

2. Which of the following is a correct way to obtain user consent under GDPR?

easy

A. Collecting data first, then asking for consent later

B. Pre-checked boxes that users can uncheck anytime

C. Assuming consent if the user visits the website

D. Clear opt-in with explicit user action before data collection

Solution

1. Step 1: Review GDPR consent rules

   Consent must be freely given, specific, informed, and unambiguous with clear user action.

2. Step 2: Evaluate options

   Only Clear opt-in with explicit user action before data collection describes explicit opt-in before data collection, which is GDPR compliant.

3. Final Answer:

   Clear opt-in with explicit user action before data collection -> Option D

4. Quick Check:

   Consent = explicit opt-in [OK]

Hint: Consent requires clear opt-in, not assumptions [OK]

Common Mistakes:

• Using pre-checked boxes as valid consent
• Assuming visiting equals consent
• Collecting data before consent

3. Consider a system that stores user data with a 'right to be forgotten' feature. Which action correctly implements this under GDPR?

def delete_user_data(user_id):
    # Step 1: Mark user data as deleted
    database.mark_deleted(user_id)
    # Step 2: Remove data from active systems
    cache.remove(user_id)
    # Step 3: Permanently erase data after retention period
    schedule_permanent_delete(user_id, days=30)

medium

A. This implementation violates GDPR because data is not deleted immediately

B. This implementation is incorrect because it does not notify the user

C. This implementation respects GDPR by delaying permanent deletion for 30 days

D. This implementation is incorrect because it does not encrypt user data

Solution

1. Step 1: Understand GDPR's 'right to be forgotten'

   GDPR allows data to be deleted but permits a retention period for legal or operational reasons.

2. Step 2: Analyze code steps

   Data is marked deleted, removed from active use, and scheduled for permanent erase after 30 days, which is acceptable.

3. Final Answer:

   This implementation respects GDPR by delaying permanent deletion for 30 days -> Option C

4. Quick Check:

   Right to be forgotten allows retention delay [OK]

Hint: Deletion can be delayed for legal retention [OK]

Common Mistakes:

• Expecting immediate permanent deletion always
• Confusing notification with deletion requirements
• Thinking encryption replaces deletion

4. A system logs user IP addresses without anonymization. Which GDPR compliance issue does this cause?

log_user_access(user_id, ip_address):
    logs.save({'user': user_id, 'ip': ip_address, 'time': now()})

medium

A. It violates data minimization by storing unnecessary personal data

B. It violates consent because IP addresses are not encrypted

C. It violates breach notification rules by logging IPs

D. It violates data portability by not exporting IP addresses

Solution

1. Step 1: Identify GDPR principles involved

   Data minimization requires only collecting data necessary for the purpose.

2. Step 2: Analyze IP logging

   Storing full IP addresses without anonymization may be unnecessary and excessive, violating minimization.

3. Final Answer:

   It violates data minimization by storing unnecessary personal data -> Option A

4. Quick Check:

   Data minimization = minimal necessary data [OK]

Hint: Store only data you really need [OK]

Common Mistakes:

• Confusing encryption with consent
• Mixing breach notification with logging
• Thinking data portability applies here

5. You are designing a system to comply with GDPR. Which combination of features best supports compliance?

• 1. Data encryption at rest and in transit
• 2. User consent management with audit logs
• 3. Automatic data deletion after user request
• 4. Collecting all user data for analytics without opt-out

hard

A. Features 1, 2, and 3 only

B. Features 2 and 4 only

C. Features 1 and 4 only

D. All features 1, 2, 3, and 4

Solution

1. Step 1: Evaluate each feature for GDPR compliance

   Feature 1 (encryption) protects data; Feature 2 manages consent properly; Feature 3 respects user deletion rights; Feature 4 violates consent and data minimization.

2. Step 2: Select compliant combination

   Only features 1, 2, and 3 together support GDPR compliance fully.

3. Final Answer:

   Features 1, 2, and 3 only -> Option A

4. Quick Check:

   Consent + encryption + deletion = GDPR compliance [OK]

Hint: Exclude features violating consent or data minimization [OK]

Common Mistakes:

• Including data collection without opt-out
• Ignoring encryption importance
• Overlooking user deletion rights