Data privacy and compliance (GDPR) in HLD - Architecture Diagram

System Overview - Data privacy and compliance (GDPR)

This system ensures that user data is handled according to GDPR rules. It manages user consent, data access, and deletion requests while protecting privacy. The system also logs all data processing activities for compliance audits.

Architecture Diagram

User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  +--------------------+--------------------+
  |                    |                    |
Consent Service    Data Processing Service     Audit Logging Service
  |                    |                    |
  v                    v                    v
Consent DB         Encrypted DB         Audit DB
  |
  v
Cache (for consent status)

Components

User

actor

Person interacting with the system, providing consent and data requests

Load Balancer

load_balancer

Distributes incoming requests evenly to API Gateway instances

API Gateway

api_gateway

Central entry point that routes requests to appropriate services and enforces security

Consent Service

service

Manages user consent records and consent status

Data Processing Service

service

Handles user data operations like access, update, and deletion with encryption

Audit Logging Service

service

Records all data processing activities for compliance auditing

Consent DB

database

Stores user consent information securely

Encrypted DB

database

Stores user personal data encrypted at rest

Audit DB

database

Stores immutable logs of data processing events

Cache (for consent status)

cache

Speeds up consent status checks to reduce latency

Request Flow - 13 Hops

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Cache (for consent status)

Cache (for consent status) → API Gateway

API Gateway → Consent Service

Consent Service → Consent DB

Consent Service → Cache (for consent status)

API Gateway → Data Processing Service

Data Processing Service → Encrypted DB

Data Processing Service → Audit Logging Service

Audit Logging Service → Audit DB

API Gateway → Load Balancer

Load Balancer → User

Failure Scenario

Component Fails:Consent DB

Impact:Consent Service cannot verify or update user consent, blocking data access or updates to comply with GDPR

Mitigation:Use database replication and failover to a standby Consent DB instance; cache consent status to serve recent requests temporarily

Architecture Quiz - 3 Questions

Which component is responsible for routing user requests to the correct service?

A Consent Service

B API Gateway

C Load Balancer

D Audit Logging Service

Design Principle

This architecture uses layered services with caching and encryption to ensure GDPR compliance. It separates consent management, data processing, and auditing to maintain clear responsibilities and secure data handling. Caching improves performance while audit logs provide traceability for compliance.

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