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Sovereign Sky
Cloud Sovereignty
Migration Roadmap

A sample roadmap for migrating business critical applications from US Hyperscalers to a European Sovereign Cloud

Sovereign Sky Advisory Services

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This roadmap outlines a 24-month strategic migration of business-critical applications from AWS and Microsoft Azure to European sovereign cloud providers. The phased approach prioritizes regulatory compliance, operational continuity, and risk mitigation while building internal capabilities for long-term cloud sovereignty.

 

Current State: 47 business-critical applications on AWS (60%) and Azure (40%)

 

Target State: 100% on European sovereign cloud infrastructure (OVHcloud, Scaleway, ionos)

 

Timeline: 24 months across 4 phases

 

Applications in Scope: ERP system, supply chain management, customer data platform, financial systems, HR platform

 

Migration Principles

1. Compliance-First Approach

  • Prioritize applications with highest GDPR, DORA, and NIS2 regulatory exposure

  • Address active regulatory concerns before deadline-driven migrations

  • Maintain continuous compliance throughout transition

 

2. Zero Business Disruption

  • Execute migrations during maintenance windows

  • Implement comprehensive testing and rollback procedures

  • Maintain parallel environments during critical transitions

 

3. Capability Building

  • Develop internal expertise in European cloud platforms

  • Transfer knowledge from system integrators to internal teams

  • Establish sustainable sovereign cloud operations

 

4. Cost Optimization

  • Leverage migration opportunity to rationalize and modernize

  • Negotiate favorable terms with European providers

  • Eliminate redundant systems and optimize licensing

 

Phase 1: Foundation & Quick Wins (Months 1-6)

Objectives

Establish governance, build capabilities, address immediate compliance gaps, and demonstrate early success

 

Key Activities

Governance & Planning (Months 1-2)

  • Establish Cloud Sovereignty Program Office with executive sponsorship

  • Define migration policies, standards, and success criteria

  • Complete detailed application assessments and dependency mapping

  • Select European cloud providers and finalize commercial agreements

  • Assemble migration team (internal + system integrator partners)

 

Quick Win Migrations (Months 3-6)

  • HR Platform Migration (Month 3-4)

    • Low complexity SaaS-like application

    • 15,000 employee records requiring EU data residency

    • Migrate from Azure to OVHcloud EU region

    • Demonstrate migration playbook and build team confidence

  • Development & Test Environments (Month 4-6)

    • Non-production workloads across multiple applications

    • Lower risk opportunity to validate technical approach

    • Migrate to Scaleway for cost optimization

    • Train technical teams on European platforms

 

Capability Building

  • Technical training on OVHcloud, Scaleway, and ionos platforms

  • Develop migration playbooks and runbooks

  • Establish DevOps pipelines for European cloud environments

  • Deploy monitoring and observability tooling

 

Deliverables

  • Cloud Sovereignty Program Office operational

  • 2 applications successfully migrated

  • Migration playbooks and standards documented

  • Team trained and confident on European platforms

  • Early risk mitigation and lessons learned

 

Success Metrics

  • Zero business disruption during migrations

  • 100% data residency compliance for migrated applications

  • Team capability scores improved by 40%

  • Migration playbook validated and refined

 

Phase 2: Core Business Systems (Months 7-14)

Objectives

Migrate highest-priority business-critical applications with careful planning and risk management

 

Key Activities

ERP System Migration (Months 7-11)

  • Current: SAP ECC on AWS (Frankfurt region)

  • Target: SAP S/4HANA on OVHcloud Sovereign Cloud

  • Complexity: High - 250 integrations, 8TB database, 5,000 users

 

Migration Approach:

  • Month 7-8: Complete detailed technical assessment and architecture design

  • Month 8-9: Build new OVHcloud environment; establish network connectivity

  • Month 9-10: Data migration (multiple rehearsals); integration reconfiguration

  • Month 10-11: Comprehensive testing (UAT, performance, disaster recovery)

  • Month 11: Phased cutover (pilot users → full deployment)

 

Financial Systems Migration (Months 10-14)

  • Current: Financial consolidation and reporting suite on Azure

  • Target: ionos Sovereign Cloud (German data center)

  • Regulatory Driver: DORA compliance requirements

  • Approach: Parallel run for one financial quarter before final cutover

 

Supply Chain Management Migration (Months 12-14)

  • Current: Custom supply chain platform on AWS

  • Target: Scaleway Dedibox for compute-intensive workloads

  • Opportunity: Application modernization and containerization during migration

 

Risk Management

  • Maintain parallel AWS/Azure environments for 30 days post-cutover

  • Executive steering committee checkpoint before each major cutover

  • 24/7 war room support during cutover weekends

  • Comprehensive rollback procedures tested and documented

 

Deliverables

  • ERP system fully sovereign and DORA-compliant

  • Financial systems meeting regulatory requirements

  • Supply chain platform modernized and migrated

  • Migration best practices refined and documented

 

Success Metrics

  • <2 hours unplanned downtime across all migrations

  • 100% integration functionality restored

  • Financial close executed successfully on new platform

  • Regulatory compliance validated by internal audit

 

Phase 3: Customer-Facing Systems (Months 15-20)

Objectives

Migrate customer data platforms and digital channels ensuring performance and user experience

 

Key Activities

Customer Data Platform (Months 15-18)

  • Current: Customer 360 platform on AWS (multi-region)

  • Target: OVHcloud with EU-only data residency

  • Data Volume: 45 million customer records, 15TB with strict GDPR requirements

  • Challenge: Real-time data synchronization with 23 touchpoint systems

 

Migration Approach:

  • Implement streaming data replication from AWS to OVHcloud

  • Gradual traffic shift (10% → 25% → 50% → 100% over 4 weeks)

  • Extensive performance testing under peak loads

  • Customer communications regarding data sovereignty improvements

 

E-Commerce Platform Migration (Months 18-20)

  • Current: Custom e-commerce on Azure (West Europe)

  • Target: Multi-cloud European architecture (OVHcloud + Scaleway CDN)

  • Requirements: <200ms page load times, 99.99% availability

  • Approach: Blue-green deployment with instant rollback capability

 

Performance Optimization

  • Implement caching strategies optimized for European providers

  • Deploy CDN with European nodes for static content

  • Database query optimization for new infrastructure

  • Load testing at 150% peak capacity before go-live

 

Deliverables

  • Customer data platform fully GDPR-compliant on European infrastructure

  • E-commerce platform maintaining SLA targets on sovereign cloud

  • Customer-facing performance maintained or improved

  • Zero customer-impacting incidents during migration

 

Success Metrics

  • Customer data 100% resident in EU with full sovereignty

  • E-commerce performance metrics maintained (≥baseline)

  • Customer satisfaction scores unchanged or improved

  • Zero data breaches or GDPR incidents

 

Phase 4: Optimization & Decommissioning (Months 21-24)

Objectives

Complete remaining migrations, optimize new environment, decommission legacy infrastructure

 

Key Activities

Remaining Application Migrations (Months 21-22)

  • 6 remaining Tier 2 business applications

  • Legacy systems with limited business value (consolidate where possible)

  • Archive-only systems (migrate to cold storage on European providers)

 

Infrastructure Optimization (Months 21-24)

  • Right-size compute and storage based on actual usage patterns

  • Implement cost optimization recommendations

  • Deploy advanced automation and infrastructure-as-code

  • Establish FinOps practices for ongoing cost management

 

Legacy Infrastructure Decommissioning (Months 22-24)

  • Systematic shutdown of AWS and Azure resources

  • Data validation and compliance verification before deletion

  • Final data exports and archival for retention requirements

  • Contract termination and financial reconciliation

  • Reclaim cost savings (estimated 15-25% reduction in cloud spend)

 

Knowledge Transfer & Handover (Month 24)

  • Complete documentation of new architecture and operations

  • Transfer all operational responsibilities to internal teams

  • System integrator knowledge transfer and training

  • Establish ongoing managed services agreement (if needed)

 

Continuous Improvement

  • Establish Cloud Center of Excellence for sovereign cloud

  • Implement continuous compliance monitoring

  • Deploy automated sovereignty attestation and reporting

  • Regular sovereignty assessments and optimization reviews

 

Deliverables

  • 100% business-critical applications on European sovereign cloud

  • Legacy US hyperscaler infrastructure fully decommissioned

  • Optimized cost structure with ongoing governance

  • Internal team fully capable of managing sovereign cloud operations

  • Compliance documentation for regulatory stakeholders

 

Success Metrics

  • Zero applications remaining on US hyperscaler infrastructure

  • Cloud spend reduced by 15-25% through optimization

  • Internal team operating environment independently

  • Regulatory compliance validated and documented

  • Board and regulator confidence in sovereignty posture

 

Risk Management Framework

Critical Success Factors

Executive Sponsorship: C-level champion with authority to remove blockers and make decisions
Adequate Resourcing: Dedicated migration team with backfill for business-as-usual work
Provider Partnership: Close collaboration with European cloud providers for escalation support
Change Management: Comprehensive stakeholder communication and training programs
Testing Rigor: No compromises on testing; schedule slips acceptable, quality failures not

 

Key Risks & Mitigations

RiskImpactMitigation

Provider capability gapsHighMulti-provider strategy; detailed upfront assessment

Data migration failuresCriticalMultiple rehearsals; validated backup/restore procedures

Integration breakageHighComprehensive integration testing; parallel running

Skills shortagesMediumEarly training; system integrator partnership; knowledge transfer

Business resistanceMediumExecutive sponsorship; clear business case; change management

Cost overrunsMediumContingency budget (20%); monthly financial reviews

Schedule delaysMediumBuffer time between phases; critical path management

 

Governance & Communication

Steering Committee: Monthly executive review (CIO, CFO, CRO, CISO)
Program Management Office: Weekly status reporting and risk management
Technical Working Group: Bi-weekly coordination across migration teams
Business Stakeholder Updates: Monthly progress communications
Board Updates: Quarterly governance reporting on compliance posture

 

Investment & Business Case

Total Program Effort

  • Migration Services: System integrator support for complex migrations

  • Internal Labor: Dedicated team (8 FTE for 24 months)

  • Training & Enablement: Platform training and certification programs

  • Tools & Automation: Migration tools, testing environments, monitoring

  • Contingency: 20% buffer for unforeseen complexity

 

Expected Benefits (3-Year)

  • Regulatory Risk Reduction: Avoid potential €50M+ GDPR/DORA penalties

  • Operational Risk Reduction: Eliminate geopolitical and jurisdictional risks

  • Strategic Value: Access to EU government and regulated sector contracts

  • Cost Optimization: 15-25% cloud spend reduction through rationalization

  • Reputation Value: Market leadership in data sovereignty and European values

 

Return on Investment

Strong positive ROI driven primarily by risk avoidance and strategic positioning, with secondary benefits from cost optimization and operational improvements.

 

Conclusion

This 24-month migration roadmap provides a structured, risk-managed approach to achieving cloud sovereignty for business-critical applications. The phased methodology balances urgency (addressing compliance gaps early) with prudence (careful planning and testing for complex systems).

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Success requires executive commitment, adequate resourcing, strong partnerships with European cloud providers, and disciplined program management. Organizations completing this migration journey emerge with:

✓ Regulatory Compliance: Full alignment with GDPR, DORA, and NIS2 requirements
✓ Strategic Independence: Freedom from geopolitical and jurisdictional risks
✓ Operational Resilience: Control over critical business infrastructure
✓ European Values Alignment: Demonstrated commitment to digital sovereignty
✓ Competitive Advantage: Positioned for sovereignty-sensitive markets and contracts

 

Sovereign Sky stands ready to guide your organization through this critical transformation journey.

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