gdpr-data-handling

GDPR Data Handling

Practical implementation guide for GDPR-compliant data processing, consent management, and privacy controls.

When to Use This Skill

• Building systems that process EU personal data
• Implementing consent management
• Handling data subject requests (DSRs)
• Conducting GDPR compliance reviews
• Designing privacy-first architectures
• Creating data processing agreements

Core Concepts

1. Personal Data Categories

Category	Examples	Protection Level
Basic	Name, email, phone	Standard
Sensitive (Art. 9)	Health, religion, ethnicity	Explicit consent
Criminal (Art. 10)	Convictions, offenses	Official authority
Children's	Under 16 data	Parental consent

2. Legal Bases for Processing

Article 6 - Lawful Bases:
├── Consent: Freely given, specific, informed
├── Contract: Necessary for contract performance
├── Legal Obligation: Required by law
├── Vital Interests: Protecting someone's life
├── Public Interest: Official functions
└── Legitimate Interest: Balanced against rights

3. Data Subject Rights

Right to Access (Art. 15)      ─┐
Right to Rectification (Art. 16) │
Right to Erasure (Art. 17)       │ Must respond
Right to Restrict (Art. 18)      │ within 1 month
Right to Portability (Art. 20)   │
Right to Object (Art. 21)       ─┘

Implementation Patterns

Pattern 1: Consent Management

// Consent data model
const consentSchema = {
  userId: String,
  consents: [
    {
      purpose: String, // 'marketing', 'analytics', etc.
      granted: Boolean,
      timestamp: Date,
      source: String, // 'web_form', 'api', etc.
      version: String, // Privacy policy version
      ipAddress: String, // For proof
      userAgent: String, // For proof
    },
  ],
  auditLog: [
    {
      action: String, // 'granted', 'withdrawn', 'updated'
      purpose: String,
      timestamp: Date,
      source: String,
    },
  ],
};

// Consent service
class ConsentManager {
  async recordConsent(userId, purpose, granted, metadata) {
    const consent = {
      purpose,
      granted,
      timestamp: new Date(),
      source: metadata.source,
      version: await this.getCurrentPolicyVersion(),
      ipAddress: metadata.ipAddress,
      userAgent: metadata.userAgent,
    };

    // Store consent
    await this.db.consents.updateOne(
      { userId },
      {
        $push: {
          consents: consent,
          auditLog: {
            action: granted ? "granted" : "withdrawn",
            purpose,
            timestamp: consent.timestamp,
            source: metadata.source,
          },
        },
      },
      { upsert: true },
    );

    // Emit event for downstream systems
    await this.eventBus.emit("consent.changed", {
      userId,
      purpose,
      granted,
      timestamp: consent.timestamp,
    });
  }

  async hasConsent(userId, purpose) {
    const record = await this.db.consents.findOne({ userId });
    if (!record) return false;

    const latestConsent = record.consents
      .filter((c) => c.purpose === purpose)
      .sort((a, b) => b.timestamp - a.timestamp)[0];

    return latestConsent?.granted === true;
  }

  async getConsentHistory(userId) {
    const record = await this.db.consents.findOne({ userId });
    return record?.auditLog || [];
  }
}