Migrating Microapps to a Sovereign Cloud: Technical Migration Plan and Pitfalls

Hook: Why moving microapps to a sovereign cloud is urgent — and hard

You ship microapps fast, but regulation and customer expectations now demand that sensitive data and identity remain within EU borders. That means moving services, CI/CD runners, logs, and data flows into the new AWS European Sovereign Cloud. The technical challenge isn't simply copying buckets — it's redesigning network boundaries, identity flows, and deployment pipelines so your apps still move fast while staying sovereign.

Executive summary (what you'll get)

This article gives a concrete, step-by-step migration plan for microapps to the AWS European Sovereign Cloud (launched Jan 2026), including network architecture, identity/federation changes, data transfer patterns, CI/CD adjustments, a practical cutover plan, and a catalogue of common pitfalls with mitigations. Use the checklists and command snippets as a working playbook. For governance and repo-level controls that tie into this plan, see notes on developer productivity and governance.

Context and trends (2026): Why sovereign cloud matters now

In late 2025 and early 2026 the EU accelerated policies and corporate procurement requirements around data residency and operational control. AWS introduced the AWS European Sovereign Cloud to provide physically and logically separate infrastructure inside the EU with tailored controls for data sovereignty. Expect increased legal and procurement pressure to host personal data, logs, and identity artifacts within a sovereign boundary — especially for regulated sectors and public-sector contracts. Operationally this pushes teams to adopt observability and audit-first patterns earlier in the migration lifecycle.

High-level migration phases

1. Assess and inventory
2. Design target architecture
3. Proof of concept (PoC)
4. Build and configure platform services
5. Data migration and validation
6. Cutover and monitoring
7. Decommission and compliance evidence

Phase 1 — Assess and inventory (1–2 weeks)

Start with a precise inventory. You need to know what touches non-EU infrastructure today and which components store or process personal data.

• Application map: list microapps, services, third-party integrations, and dependencies.
• Data classification: PII, regulated data, logs, telemetry — assign a sensitivity level.
• Network flows: capture source/destination IPs, ports, protocols. Use VPC Flow Logs and service maps (Istio/Linkerd if used).
• Identity flows: what IdP, SAML/OIDC endpoints, SCIM provisioning, SSH and service accounts are active?
• CI/CD and secrets: where are runners, agents and secret stores located? Link your findings to CI/CD governance playbooks such as From Micro-App to Production.
• Volumes and transfer sizes: estimate TBs to move and the allowable downtime window.

Deliverables

• CSV inventory of apps and dependencies
• Migration risk matrix (data sensitivity × time to migrate)

Phase 2 — Design target architecture

The sovereign cloud is physically and logically separate. Treat it as an independent AWS partition/region for design purposes. Your design must keep sensitive data and control planes inside the sovereign boundary.

Network architecture (recommended pattern)

• Transit architecture: use a Transit Gateway or Transit VPC equivalent inside the sovereign cloud to centralize routing. Isolate dev/test/prod via separate VPCs and accounts (AWS Organizations structure).
• Subnets: Public load-balancer subnets, private app subnets, private data subnets with no internet gateway. Use NAT Gateway or Egress VPC Endpoints inside the sovereign cloud for controlled outbound access.
• Service endpoints: prefer VPC Interface Endpoints (AWS PrivateLink) for S3, ECR, Secrets Manager, KMS, DataSync where supported by the sovereign cloud. Confirm endpoint service names and region-specific DNS.
• Connectivity: use AWS Direct Connect hosted in EU locations or an IPsec VPN terminating into the sovereign cloud. Verify physical Direct Connect presence for the sovereign region — if unavailable, plan high-bandwidth 'sneakernet' (Snowball Edge / edge appliances) for bulk data.

Identity and access

Identity is the most common migration gotcha: federation endpoints, SCIM provisioning, and audit logs must remain inside the sovereign boundary.

• Host your IdP either inside the EU or use a vendor contract guaranteeing EU data residency. If you use a cloud IdP outside the EU, obtain a legal/technical assurance that identity tokens and user data do not leave the EU. For a technical risk breakdown of identity in financial services and highly regulated contexts, see Why Banks Are Underestimating Identity Risk.
• Use AWS Identity Center (or an equivalent identity service deployed in the sovereign cloud) to provide SSO and manage cross-account roles. If you rely on SAML/OIDC federation, ensure metadata endpoints and assertions transit only via EU-resident infrastructure.
• Recreate critical IAM roles and policies inside the sovereign accounts. Avoid cross-region trust to non-sovereign accounts for administrative access.
• Key management: create customer-managed KMS keys in the sovereign cloud; consider importing existing keys if allowed and compliant. Be aware of cross-account and partition encryption traps covered in security post-mortems.

CI/CD and pipelines

• Run CI runners inside the sovereign cloud. For GitHub Actions or GitLab, use self-hosted runners deployed on EKS or EC2 inside the sovereign accounts; for best practices on taking micro-apps through CI/CD into production see From Micro-App to Production.
• Store secrets in sovereign Secrets Manager or Vault; rotate and audit keys as part of the pipeline.
• Update pipelines to push images/artifacts to sovereign ECR registries and to deploy to the sovereign Kubernetes/ECS clusters. Consider caching and edge artifact strategies alongside cache and registry performance guidance.

Phase 3 — Proof of concept (2–4 weeks)

Build a minimal, fully sovereign stack that represents the critical path: identity authentication, a microapp, storage, logging, and CI deploy.

• Deploy a small microapp (sample microservice + database) inside the sovereign account.
• Configure federation to an EU-hosted IdP and verify login flows and SCIM provisioning.
• Test data egress controls, VPC Flow Logs, and CloudTrail and observability audits.
• Run a CI pipeline that builds, pushes to ECR (sovereign), and deploys to the sovereign cluster.

Phase 4 — Build and configure platform services

At scale you’ll automate everything. Treat this phase like a platform engineering sprint.

• Use IaC (Terraform/CloudFormation) templates scoped to the sovereign provider/region. Verify the provider endpoints and defaults for the sovereign partition and align with developer productivity and multisite governance.
• Automate account provisioning in AWS Organizations and apply SCPs that prevent accidental cross-border replication.
• Provision KMS keys, Secrets Manager, ECR repos, and EFS/RDS snapshots inside the sovereign boundary.
• Deploy monitoring stacks (Prometheus/Grafana, CloudWatch/Observability) to ensure logs and metrics stay inside the EU region.

Example Terraform snippet (VPC)

resource "aws_vpc" "app_vpc" {
  cidr_block = "10.10.0.0/16"
  tags = { Name = "sov-app-vpc" }
}

resource "aws_subnet" "private" {
  count = 3
  vpc_id = aws_vpc.app_vpc.id
  cidr_block = cidrsubnet(aws_vpc.app_vpc.cidr_block, 8, count.index)
  availability_zone = data.aws_availability_zones.available.names[count.index]
  tags = { Name = "sov-app-private-${count.index}" }
}

Phase 5 — Data migration (strategy + commands)

Data is often the longest part. Choose a hybrid approach: bulk transfer + incremental synchronization.

Options

• AWS DataSync: ideal for continuous sync of file systems and object stores — make sure the DataSync agent runs in-source and target endpoints are sovereign.
• Snowball Edge: for multi-TB or PB transfers where network throughput is limiting; ship devices to EU locations and import into sovereign S3 endpoints. See field notes on edge appliances and bulk transfer strategies at edge appliance reviews.
• S3 replication & rsync: use a two-phase copy: bulk copy, then run an incremental live sync prior to cutover. Real-world store migrations with zero-downtime cutovers are good reference points (example case studies at store launch migrations).

CLI examples

Copy S3 objects to sovereign S3 (replace --endpoint-url if the sovereign API uses custom endpoints):

aws s3 sync s3://source-bucket/ s3://sov-bucket/ --source-region eu-west-1 --region eu-sov-1 --delete

# Or with explicit endpoint (if provider requires it)
aws s3 sync s3://source-bucket/ s3://sov-bucket/ --endpoint-url https://s3.eu-sov-1.amazonaws.com

Data integrity and validation

• Use checksums and object counts: compare manifests before and after.
• Perform sample restores for databases, validate schema and application behavior.
• For transactional stores, use change data capture (CDC) to replicate deltas until cutover.

Phase 6 — Cutover plan (the critical path)

A cutover must be orchestrated, short, and reversible. The typical window: reduce downtime via DNS TTL management, final incremental sync, freeze writes, switch endpoints, and verify traffic.

Pre-cutover checklist (48–72h)

• Reduce DNS TTLs to 60 seconds or lower.
• Notify stakeholders and schedule maintenance windows.
• Ensure final replication tasks are running and near zero delta.
• Create a complete snapshot/backups and export manifests.
• Confirm CI runners, artifact registries, and secrets are available in the sovereign cloud.

Cutover steps (hour 0 — hour +2)

1. Freeze writes (application-level): place service into read-only if possible, or enable a maintenance mode.
2. Run final incremental sync for DB (CDC catch-up) and object store rsync.
3. Swap DNS records to point to sovereign ALBs or edge endpoints.
4. Lift maintenance mode and validate functional tests and smoke tests.
5. Monitor logs, latency, and error rates for 1–4 hours intensively. Use observability dashboards and runbooks to accelerate triage.

Rollback plan

• Rollback is primarily DNS revert and re-enable writes to original systems.
• Keep the original infrastructure live, in read-only or standby mode, until post-cutover validation completes (minimum 48–72h).

Phase 7 — Post-cutover and decommission

• Run full post-mortem and evidence collection for compliance audits (CloudTrail logs, access records). Use observability and auditing guidance from Observability in 2026.
• Decommission old cloud resources only after legal and business signoff; preserve snapshots for the defined retention period.
• Deliver a compliance pack: architecture diagrams, access logs, key custodian lists, and data flow statements.

Common pitfalls and how to avoid them

Pitfall 1: Identity federation breaks

If your IdP endpoints are outside the EU, authentication flows may violate policies or experience latency and routing issues. Solution: deploy IdP instances inside EU or use contractually bounded IdP that guarantees EU residency for identity assertions. Test SAML/OIDC metadata validity and token lifetimes after migration. See identity risk analysis at Why Banks Are Underestimating Identity Risk.

Pitfall 2: CI/CD agents run outside sovereign boundary

If pipeline runners execute outside the sovereign cloud, build artifacts or secrets can leak. Solution: move runners into sovereign accounts and use private artifact registries. For GitHub/GitLab, use self-hosted runners on sovereign VMs or containers and follow CI/CD governance patterns in From Micro-App to Production.

Pitfall 3: Third-party services store data outside the EU

Many SaaS integrations (analytics, APM, error reporting) default to non-EU endpoints. Audit all integrations and either configure EU endpoints or replace them with sovereign-compliant alternatives. Consider in-sov hosted proxies for third-party APIs if contractual movement is infeasible. Security takeaways for third-party telemetry and auditing are discussed in adtech security post-mortems.

Pitfall 4: Missing service availability or AMIs in sovereign cloud

Some marketplace AMIs, managed services, or partner solutions might not be immediately available in the new sovereign region. Inventory required AMIs and prepare to build custom images or use containerized alternatives. Evaluate edge-friendly images and appliances as a fallback (see edge appliance reviews).

Pitfall 5: KMS and cross-account encryption traps

KMS keys can't be trivially shared across partitions. Recreate or import keys into the sovereign cloud and update encryption configurations. Validate backup and restore with the new keys before cutover. For broader architecture patterns to survive multi-provider failures, review building resilient architectures.

Operational checks and observability

• Enable VPC Flow Logs, CloudTrail, and audit trails in the sovereign accounts immediately. Tie these into modern observability platforms: see observability guidance.
• Run synthetic transactions to validate the authentication, authorization, and data path for each microapp.
• Define SLOs and set alerts around latency and error rates that may signal cross-border leakage.

Sample timeline for a medium-sized microapp portfolio (10–20 apps)

1. Week 0–2: Assess & inventory
2. Week 3–4: Design and PoC (2–3 apps)
3. Week 5–8: Build platform services and CI runners
4. Week 9–12: Data migration waves and testing
5. Week 13: Cutover for first production app, then iterate weekly

Advanced strategies for lower downtime

• Blue/Green deployments: keep green environment in sovereign cloud then shift traffic via DNS/ALB routing. Pattern guidance for resilient backends is explored in resilient backends playbooks.
• Canary traffic splitting: direct a small percentage of users to the sovereign cloud to validate behavior before full cutover.
• Edge proxy with request filtering: for APIs that call third-party services, run an EU-resident edge proxy to minimize outbound flows and apply data scrubbing policies.

Checklist: What to verify before you sign off

• All regulated data resides in sovereign accounts and storage.
• Primary IdP and provisioning are within the EU or covered by EU residency contract.
• CI/CD runners and artifact registries are inside the sovereign cloud. See CI/CD and governance notes at From Micro-App to Production.
• Cryptographic keys are managed inside sovereign KMS; backups encrypted with in-sov keys.
• Routing, DNS, and egress filters configured to prevent accidental cross-border calls.
• Monitoring and audit logs retained according to policy and available for spot checks.

Real-world example (summary)

A fintech scale-up with 12 customer-facing microapps moved to the AWS European Sovereign Cloud in Q1 2026. They ran a 6-week PoC using a single account scaffold, migrated CI runners and ECR, and used Snowball Edge for 150 TB of historical transaction logs (field references on edge appliances are helpful: edge appliance review). The cutover used a canary approach across two customer clusters, and the firm avoided legal complications by keeping their IdP and SCIM provisioning inside the EU. Post-migration they reduced procurement risk and passed a customer audit with a 24-hour evidence package pulled from sovereign CloudTrail trails. For similar zero-downtime migration case studies see store launch migrations.

Final recommendations

• Start small with a PoC — prove identity, CI, and a simple data migration end-to-end. Reference CI/CD playbooks such as From Micro-App to Production.
• Automate everything — IaC, tests, and pipelines reduce human error during cutover. Developer productivity patterns are documented in Developer Productivity and Cost Signals.
• Keep a short rollback window — maintain the old environment briefly to enable quick reversion if needed.
• Involve legal and security early to validate contractual controls for IdP and third-party services.
• Document and retain artifacts for compliance — architecture diagrams, CloudTrail logs, and migration manifests are evidence gold.

"Treat the sovereign cloud as a new operating boundary — design and test for it, don’t assume connectivity or policy parity with your existing cloud."

Call to action

Ready to move your microapps to the AWS European Sovereign Cloud with minimal risk? Start with a focused 2-week PoC: we can help map your identity flows, validate CI/CD runner placement, and create a data migration blueprint. Contact us for a tailored migration plan and compliance pack.

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