Consent, Retention, and Opt-Out at Scale

Subtitle: How to Handle Opt-Outs, Suppression, and Deletion Requests Across Contact Matching Systems

Processing user contacts means you also inherit data subject rights obligations—even from people who haven’t signed up yet.

If you process it, you owe it protections. This fundamental principle applies to all personal data that flows through your contact matching systems, regardless of whether the individual has a direct relationship with your platform.

This article explains how to handle consent tracking, data retention, and opt-outs systematically for Find Your Friends and referral features, with specific guidance for implementing these systems at scale.

Core Foundation

This article continues from:
Safe Contact Import

Supporting articles:

• The Consent Playbook
• Post-Send Obligations

Key Systems You Must Build

Effective management of consent, retention, and opt-outs requires several interconnected systems:

System	Purpose	Implementation Considerations
Consent tracking	Record permission given before matching or messaging	Secure, tamper-evident storage; comprehensive logging; audit capabilities
Retention controls	Delete data when no longer needed	Automated deletion workflows; configurable retention periods; deletion verification
Suppression lists	Block future invites or matching	Global, cross-user application; secure hashing; efficient lookup
Data subject request handling	Honor opt-out, deletion, and access rights	Request verification; timely processing; comprehensive coverage

Critical Requirement: These systems must work for both users and non-users. Many platforms make the mistake of only implementing these controls for registered users, creating significant compliance gaps for non-user data subjects.

How to Handle Consent at Scale

Consent management is the foundation of compliant contact matching systems. It creates both legal protection and user trust.

1. Log Consent at Action Points

Comprehensive consent logging creates accountability and provides evidence of compliance.

Implementation Guidance:

• Log These Elements for Each Critical Action:

  • User ID who initiated the action
  • Precise timestamp with timezone
  • Consent checkbox status (checked/unchecked)
  • Selected contacts (securely hashed)
  • Exact consent text shown to the user
  • IP address and device information
  • Action type (matching, inviting, etc.)

• Technical Implementation:

  • Use append-only, tamper-evident storage for consent records
  • Implement proper access controls and encryption
  • Create backup and recovery procedures for consent logs
  • Design for efficient querying during compliance investigations

• Documentation Requirements:

  • Document your consent collection methodology
  • Create a consent verification process
  • Maintain records of consent text changes over time
  • Establish retention periods for consent records

Example Implementation:

{
  "consent_id": "c123456789",
  "user_id": "u987654321",
  "timestamp": "2025-04-29T18:24:30Z",
  "consent_text": "I confirm I have permission to match or invite these contacts.",
  "consent_given": true,
  "action_type": "contact_matching",
  "selected_contacts": [
    "a94a8fe5ccb19ba61c4c0873d391e987982fbbd3", // Hashed email
    "c3499c2729730a7f807efb8676a92dcb6f8a3f8f"  // Hashed email
  ],
  "ip_address": "192.168.1.1",
  "user_agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64)..."
}

2. Allow Consent Withdrawal Easily

Respecting users’ right to withdraw consent is both a legal requirement and a trust-building feature.

Implementation Guidance:

• User Controls

  • Let users revoke permission to match/import at any time
  • Reflect revocation immediately in your matching engine
  • Provide clear feedback about the effect of withdrawal
  • Implement granular controls for different types of processing

• Technical Implementation:

  • Create a consent status database with real-time updates
  • Check consent status before any matching or invitation action
  • Implement cascading deletion for revoked consent
  • Log consent withdrawal events with timestamps

• User Experience Considerations:

  • Make consent controls easily discoverable in privacy settings
  • Use clear, non-technical language to explain effects
  • Provide confirmation of successful withdrawal
  • Consider offering partial withdrawal options

Example Interface:
A “Privacy Controls” section in user settings with toggles for:

• “Match my contacts with existing users” (ON/OFF)
• “Allow me to invite contacts” (ON/OFF)
• “Delete all previously imported contacts” (button)

Legal Alignment:
This approach satisfies GDPR Article 7(3) requirements for consent withdrawal and demonstrates respect for user autonomy.

How to Handle Retention at Scale

Implementing appropriate retention periods is essential for compliance with data minimization principles and reduces risk.

Implementation Guidance:

Data Type	Retention Window	Technical Implementation
Imported contacts (unmatched)	Delete after session ends	Client-side only; no server persistence
Imported contacts (matched)	Keep 30–60 days unless user converts	TTL-based storage; scheduled deletion jobs
Invitation records	6-12 months for compliance documentation	Archived storage with access controls
Suppression entries	Retain hashed records indefinitely for compliance	Secure, indexed database; regular integrity checks

Key Principle: No silent retention of unmatched or uninvited contacts. Data should only be retained for as long as necessary to fulfill the specific purpose for which it was collected.

Technical Implementation:

• Automated Deletion Workflows

  • Implement database TTL features when available
  • Create scheduled jobs for data purging
  • Log all deletion activities for audit purposes
  • Implement verification to confirm successful deletion

• Retention Policy Management

  • Document retention periods and their justification
  • Create processes for reviewing and updating retention policies
  • Implement exception handling for legal holds
  • Design for compliance with varying regional requirements

• Data Lifecycle Management

  • Implement data classification to apply appropriate retention
  • Create workflows for transitioning data between states
  • Design for secure, complete deletion
  • Consider pseudonymization for data that must be retained longer

Example Retention Policy Documentation:

Data Category: Unmatched Imported Contacts
Retention Period: Session only (not persisted server-side)
Justification: Data minimization principle; no business need beyond session
Deletion Method: Automatic session cleanup; no server storage
Exceptions: None

How to Handle Opt-Out and Suppression at Scale

Effective suppression systems are critical for honoring privacy choices and preventing unwanted communications.

1. Suppress Future Invitations or Matches

Global suppression ensures that opt-out choices are respected across all users and features.

Implementation Guidance:

• When a Recipient Unsubscribes:

  • Hash their email address (e.g., SHA-256)
  • Add it to a global suppression list
  • Check suppression before allowing future invites or matches
  • Apply suppression across all users, not just the original sender

• Technical Implementation:

  • Use consistent hashing algorithms for suppression entries
  • Implement database indexes for fast suppression checks
  • Consider bloom filters for efficient matching
  • Design for high-availability and low-latency lookups

• Operational Considerations:

  • Process opt-outs immediately (within 24 hours at most)
  • Maintain suppression records indefinitely
  • Implement monitoring for suppression system failures
  • Create backup and recovery procedures for suppression lists

Example Suppression Check Workflow:

1. User selects contacts to invite
2. Before processing, system hashes each email address
3. System checks each hash against global suppression list
4. Any suppressed contacts are filtered out
5. User is shown only non-suppressed contacts for final confirmation

2. Allow Non-Users to Opt Out

Respecting the rights of individuals who haven’t signed up for your service is crucial for compliance.

Implementation Guidance:

• Non-User Access Points

  • Provide a public form or email where non-users can:
    • Request removal from matching
    • Block future invites
    • Request deletion of any data your platform holds
  • Include opt-out links in all invitation messages
  • Create a privacy portal accessible without an account

• Verification Process

  • Implement secure verification for non-user requests
  • Balance security with accessibility
  • Document your verification approach
  • Train support staff on handling non-user requests

• Response Requirements

  • Respond within legal deadlines (typically 30 days under GDPR/CCPA)
  • Provide confirmation of actions taken
  • Maintain records of request fulfillment
  • Implement follow-up procedures for complex requests

Example Non-User Rights Request Form:
A public web form that collects:

• Email address to be suppressed/deleted
• Type of request (opt-out, deletion, access)
• Verification method (e.g., email confirmation link)
• Optional explanation field

Legal Necessity:
Both GDPR and CPRA extend rights to individuals whose data you process, regardless of whether they have an account with your service. Honoring these rights is not optional.

Regional Requirements Snapshot

Different regions have specific requirements for handling consent, retention, and opt-outs:

Region	Obligation	Implementation Requirements
GDPR (EU/UK)	Right to object to processing, right to erasure	Respond within 30 days; document basis for processing; implement complete erasure
CPRA (California)	Right to opt out of sharing, right to delete	“Do Not Sell or Share” option; deletion within 45 days; verification procedures
CASL (Canada)	Right to unsubscribe from electronic messages	Immediate unsubscribe functionality; record keeping for 3+ years
LGPD (Brazil)	Right to revoke consent and request data deletion	Respond within 15 days; document lawful basis; implement complete deletion

Global Compliance Strategy:

• Implement the strictest requirements across all regions
• Create workflows that accommodate different regional timelines
• Document your approach to each regional requirement
• Regularly review and update as regulations evolve

For more detailed information on specific privacy laws, see: Other Privacy Laws

Common Mistakes to Avoid

Certain implementation patterns create significant legal and reputational risks:

Mistake	Why It’s a Problem	Better Alternative
Not suppressing unsubscribed contacts globally	Allows repeated harassment; violates opt-out rights	Implement global, cross-user suppression; check before any new invites
Retaining unmatched imports indefinitely	Data minimization failure; increases breach risk	Implement automatic deletion after defined period; document retention policy
Ignoring non-user deletion requests	Breach of GDPR and CCPA rights; potential regulatory action	Create accessible non-user rights request process; train staff on handling
Poor consent audit trails	Inability to defend processing if audited; compliance gap	Implement comprehensive consent logging; maintain tamper-evident records
Siloed suppression lists	Allows continued contact despite opt-outs; damages trust	Create centralized suppression system; apply across all features
Manual deletion processes	Inconsistent application; human error risk	Automate deletion workflows; implement verification checks

Implementation Guidance:

• Conduct regular audits of your consent, retention, and opt-out systems
• Test the effectiveness of your suppression system
• Verify that deletion workflows are functioning correctly
• Document your approach to addressing these common pitfalls

Summary: Protect Everyone’s Rights, Not Just Users

Effective management of consent, retention, and opt-outs creates both compliance and trust:

Principle	Outcome	Business Benefit
Consent logging	Defensible processing practices	Reduced regulatory risk; evidence for compliance
Quick deletion	Reduced breach exposure	Lower security liability; simplified compliance
Non-user suppression	Respect beyond active users	Better sender reputation; fewer complaints
Global opt-outs	Strong compliance and brand trust	Improved deliverability; sustainable growth

Rights-respecting systems aren’t just nice—they’re legally mandatory. The technical infrastructure you build to manage consent, retention, and opt-outs is a critical component of your overall compliance posture.

If you build these systems properly now, you avoid urgent, expensive refactors later. More importantly, you create a foundation for ethical, sustainable growth that respects individual privacy rights regardless of whether someone is a registered user.

Up Next

Next, we’ll zoom out to show how global privacy laws specifically impact contact matching systems—and how to build universal compliance.

Read Global Rules for Contact Matching

Or revisit safe import patterns:
Safe Contact Import