Migrating to AWS European Sovereign Cloud: A Step-by-Step Runbook for European Enterprises

Hook: Why European sovereign cloud migration is urgent—and solvable

If your organization stores, processes, or backs up EU-sensitive data, you know the pressure: regulators, auditors, and customers demand demonstrable data sovereignty, stability, and cryptographic control. At the same time, business teams expect cloud elasticity and DevOps speed. The recent launch of the AWS European Sovereign Cloud (announced in January 2026) gives European enterprises a path to reconcile those demands—but only if you migrate with a disciplined, auditable runbook.

Executive summary — What this runbook delivers

This article is a step-by-step runbook for migrating sensitive workloads into the AWS European Sovereign Cloud. It combines compliance mapping, architecture decisions, data movement strategies, network peering and cutover criteria into a prescriptive playbook. Use it as your migration backbone, then adapt Terraform/CloudFormation modules and CI/CD pipelines to automate repeatable steps.

Context: 2026 trends that shape your migration

• Hyperscalers offering sovereign zones: By late 2025 and into 2026, major cloud providers introduced region-isolated offerings to meet EU sovereignty requirements—AWS’s new European Sovereign Cloud being a primary example.
• Stricter EU regulatory enforcement: NIS2, GDPR maturity, and national data-residency policies have increased audit frequency and technical evidence requirements for data processing and export controls.
• Zero-trust and confidential computing: Organisations are requiring cryptographic separation of key material inside the EU using KMS/CloudHSM and hardware-backed confidentiality.
• Hybrid and multi-cloud control planes: Teams want centralized governance while preserving data residency. Expect to run control-plane tooling in a non-exfiltrating manner or in-region equivalents.

Preparation: Define scope, stakeholders, and constraints

Start with a tight migration scope. Don’t attempt to shift everything at once. Follow this checklist to avoid scope creep:

1. Assemble the migration team: cloud architects, security/compliance officers, network engineers, app owners, SREs, and a legal reviewer.
2. Define business drivers and SLAs: RTO/RPO, latency and throughput thresholds, and regulatory constraints such as data export bans.
3. Inventory workloads and classify data: label assets as Public, Internal, Confidential, Sensitive. Use automated scanners (CMDB, agent-based discovery) and manual verification for sensitive assets.
4. Map dependencies and integrations: APIs, third-party services, CI/CD pipelines, identity providers, logging and monitoring, and backup targets.
5. Identify in-scope resources: accounts, S3 buckets, EBS volumes, databases (RDS/Aurora), IAM roles, service endpoints, and custom hardware integrations.

Compliance mapping: Translate legal requirements into technical controls

With legal and compliance in the loop, map each regulatory requirement to a technical control. Capture traceability in a matrix.

Minimum controls to map

• Data residency: Ensure data-at-rest and key material remain physically in EU-based sovereign region.
• Access controls: Enforce least privilege, role separation, and privileged access audits.
• Data export controls: Block or log any cross-border data flows and use organizational policies to prevent replication out of the sovereign region.
• Logging & auditability: Ensure immutable logs (CloudTrail, VPC Flow Logs) are stored in-region and meet retention rules.
• Encryption & KMS: Use customer-managed keys (CMKs) with EU-only key stores or CloudHSM clusters if required.

Document the compliance matrix

Create a table mapping each legal requirement to: technical control, responsible owner, evidence type (config dump, screenshot, log extract), and acceptance criteria for sign-off. This becomes your migration acceptance gate.

Architecture and account design — region isolation and governance

The sovereign cloud is logically and physically separated from other AWS regions. That means your governance and account topology must be explicit.

1. AWS Organization or equivalent: Create a dedicated AWS Organization/OU for the sovereign region. Do not rely on cross-region default org trust unless explicitly supported by the sovereign offering.
2. Account model: Use a multi-account strategy: security, shared services (bastion, logging), production workloads, non-prod, and sandbox. Ensure SCPs (Service Control Policies) lock down cross-region resource creation.
3. Network topology: Design VPCs per environment, with Transit Gateway or regional equivalents for connectivity isolation. Plan subnets per AZ and micro-segmentation rules with Network ACLs and security groups.
4. KMS & HSM: Provision CMKs in-region and, where required, dedicated CloudHSM clusters with EU residency of key material.
5. Logging: Centralize CloudTrail and S3 logging to a dedicated, access-restricted logging account in the sovereign region.

Network setup and peering — secure connectivity to on-prem and partners

Network is the backbone for a compliant migration. For sensitive workloads, prefer private connectivity over internet-based VPNs.

Recommended connectivity stack

• Direct Connect / Private Interconnect: Use AWS Direct Connect locations hosted in the EU and ensure the physical link’s endpoints and providers maintain EU data handling commitments.
• Transit Gateway: Use Transit Gateway for hub-and-spoke VPC connectivity to reduce peering complexity; enforce VPC route table segregation and route filters.
• PrivateLink: Use AWS PrivateLink for service-to-service access without exposing services to public IPs.
• VPC Peering: VPC peering is allowable between sovereign region VPCs; document peering attachments and use flow logs to monitor traffic.
• Firewall & egress control: Deploy Network Firewall or third-party virtual appliances in a centralized inspection account. Block unapproved egress destinations to prevent accidental data exfiltration.

IAM mapping and identity strategy

Identity is critical when moving into an isolated region. You must preserve least privilege and avoid identity drift.

1. Identity provider placement: Decide if identity providers (IdP) remain on-prem or if you’ll deploy a regional IdP instance. For strict sovereignty, run your IdP endpoints within the EU.
2. Role and policy migration: Extract existing IAM roles and policies; map them to new accounts using least privilege. Use Terraform or CloudFormation to recreate policies for traceability.
3. Cross-account access: Implement strict trust policies and MFA-enforced principals. Prefer short-lived credentials (STS) and OIDC where supported.
4. Privileged access management (PAM): Integrate with a PAM solution (e.g., CyberArk, HashiCorp Vault) hosted in-region for elevation workflows and session recording.

Data migration strategies

Pick the right tool for the data profile: large object stores vs. databases vs. block storage. Use a combination of online and offline transfers to balance speed, cost, and auditability.

Options and when to use them

• AWS DataSync: Best for file- and object-level data transfers over private links with built-in verification and incremental syncs.
• Database replication: Use native DB replication (e.g., logical replication for PostgreSQL, or DMS for heterogeneous migrations) and perform a final cutover after delta sync.
• Snow Family (Snowball Edge): Choose offline physical transfer for very large datasets or constrained network egress; ensure the shipment chain complies with EU sovereignty rules.
• S3 replication: When allowed, configure in-region replication or controlled CRR flows where policy permits; otherwise avoid cross-region replication that breaches residency requirements.
• Block volumes: Snapshot and copy EBS volumes, or reinitialize via rsync for smaller datasets. Validate checksums after restore.

Encryption and integrity checks

Always encrypt in transit and at rest. Use TLS 1.2+ for transfers and ensure server-side or client-side encryption keys remain in-region. For every dataset, compute cryptographic checksums (SHA-256) pre- and post-transfer and preserve audit logs.

Cutover criteria and go/no-go checklist

Define quantitative and qualitative criteria before scheduling the final cutover window. Use the following go/no-go gates as your minimum.

Mandatory cutover criteria

• Compliance attestation: Legal and compliance teams sign-off that residency and data export controls meet requirements.
• Connectivity validated: Private connectivity (Direct Connect) and fallbacks (VPN) fully tested between on-prem and sovereign region.
• Data sync status: Initial bulk copy complete and delta synchronization latency within acceptable RPO.
• Security scans passed: Static/dynamic scans, vulnerability assessments, and configuration checks (CIS benchmarks) show no critical findings.
• IAM & access tests: All production roles validated, MFA enforced, and emergency access (break-glass) procedures documented.
• Rollback plan in place: Verified backout steps including DNS rollback, revoking new region credentials, and re-pointing traffic to source.

Soft-cutover and final-sync steps

1. Schedule a freeze window for writes or switch to read-only mode on source systems where feasible.
2. Perform the final delta sync using DataSync or DB replication monitoring tools; validate record counts and checksums.
3. Lower DNS TTLs in advance (24–48 hours) to speed cutover; plan DNS change as the last network step.
4. Switch traffic to new endpoints through load balancer reconfiguration or DNS updates; keep monitoring dashboards visible to all stakeholders.

Testing plan — prove it before you trust it

Testing must be staged, automated, and repeatable. Cover functional, performance, security, and disaster recovery tests.

Essential tests

• Functional smoke tests: API, authentication, and critical path transactions for each application.
• Performance benchmarks: Latency and throughput tests under expected and peak loads (use tools like Locust, k6, or native benchmarking).
• Chaos and resilience: Simulate AZ failures, network partitions, and instance termination to validate failover works as designed.
• Security validation: Pen tests, configuration audits, and review of access logs. Verify that logs and traces remain in-region and are tamper-evident.
• Restore and DR drills: Restore a subset of data from backups and test recovery procedures to meet RTO/RPO targets.

Post-cutover — hardening, monitoring, and audit evidence

After cutover, treat the first 72 hours as a high-alert stabilization window.

• Monitoring & observability: Ensure metrics, traces, and logs feed into in-region observability stacks and that alerting is validated for on-call rotation.
• Continuous compliance: Enable automated evidence collection: config snapshots, CloudTrail exports, and policy evaluation reports for auditors.
• Cost and performance tuning: Adjust instance sizes, autoscaling policies, and storage classes to control cost without compromising compliance.
• Operational runbooks: Update incident response and runbooks to reflect new ARNs, endpoints, and support contacts.

Common migration pitfalls and how to avoid them

• Underestimating dependency mapping: Use automated dependency discovery and verification to avoid missed integration points.
• Assuming default services exist: Sovereign regions may not expose the same service catalog immediately. Validate service availability and plan fallbacks for unsupported services.
• Key material leakage: Never export private keys out of the sovereign region if your legal obligations require EU residency.
• Poor rollback planning: Always validate your rollback on a dry run and keep pre-cutover snapshots readily available.

Automation and IaC recommendations

Automate everything you can. Treat your migration as a software release:

• Use Terraform or CloudFormation modules for account provisioning, VPCs, IAM, and logging stacks.
• Store state and secrets in-region: use regional remote state backends and secrets managers to prevent configuration drift and accidental export.
• Integrate migration steps into CI pipelines and gate releases with automated tests and policy checks (policy-as-code).

Example timeline (simplified)

1. Weeks 0–2: Scope, inventory, compliance mapping, and account planning.
2. Weeks 3–6: Network setup, identity mapping, and initial account provisioning.
3. Weeks 7–10: Data seeding (bulk copy), app migration to staging, and testing.
4. Weeks 11–12: Final sync, cutover, and stabilization.

Short real-world example

One EU financial services firm we advised adopted the following approach: (1) created a dedicated organization and logging account in the sovereign region, (2) used Snowball Edge for initial bulk transfers of 200+ TB, (3) configured DataSync for delta syncs over Direct Connect, and (4) enforced CMKs with a CloudHSM cluster inside the EU. They achieved a validated cutover with RPO under 10 minutes and a complete audit trail for their regulator.

"By combining physical transfer for scale and automated delta syncing, we met both performance and strict residency needs without extended downtime." — Lead Cloud Architect, EU Financial Services

Final checklist — decision-ready

• Compliance matrix complete and signed.
• Account topology and SCPs enforced.
• Network private links validated; fallbacks tested.
• Data migration verification (checksums, counts) completed.
• IAM roles recreated and tested; break-glass procedures in place.
• Rollback plan rehearsed and approved.
• Monitoring, logging, and alerting fully operational in-region.

Next steps and recommendations

Begin with a pilot: select a single non-critical but representative workload, migrate it end-to-end using this runbook, and iterate. Use the lessons to create Terraform modules, automated test suites, and a hardened cutover checklist you can re-use across teams.

Call to action

If you’re planning a migration into the AWS European Sovereign Cloud, start with a pilot and a compliance matrix. If you want a hands-on workshop, runbook templating, or Terraform modules tailored to your environment, contact our cloud migration practice for a rapid 2-week assessment and pilot plan. Protect residency, preserve agility, and minimize downtime—migrate with confidence in 2026.

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