switching software/cloud infrastructure

Cloud Migration Rollback Plan Template (AWS/Azure/GCP)

Emergency rollback procedures for failed cloud migrations with UK compliance notes.

SaaS Migration Checklist: Cloud Provider Rollback & Transition

Target: SME Operations Leads & System Administrators (UK) Risk Level: Critical Timeline: 4–6 Weeks Team Size: 3–5 Core Members

This document outlines the systematic transition from a failed migration state to a new cloud provider. All procedures align with UK GDPR and Data Protection Act 2018 requirements.

Phase 1: Pre-Migration Planning (Week 1–3)

Assessment & Infrastructure Audit

  • Conduct a full inventory of all cloud-hosted assets, including VMs, databases, and object storage.
  • Document current egress costs and projected ingress costs for the new provider.
  • Map all dependencies between microservices to prevent breaking API calls.
  • Verify the new provider’s data centre locations meet UK data sovereignty requirements.
  • Identify all hardcoded IP addresses or endpoints in application configuration files.
  • Audit existing SSL/TLS certificate renewal cycles and export private keys where necessary.

Data Mapping & Integrity

  • Create a comprehensive data dictionary mapping source schemas to the new provider’s format.
  • Perform a test export of a subset of data to validate compatibility with the target environment.
  • Audit all PII (Personally Identifiable Information) locations to ensure encrypted transit.
  • Define the RPO (Recovery Point Objective) and RTO (Recovery Time Objective) for the migration window.
  • Validate database collation settings (e.g., UTF-8) to prevent character encoding errors.

Golden Copy Backup

  • Perform a final, full-system snapshot of the current environment.
  • Verify the checksum (SHA-256) of the backup files to ensure data integrity.
  • Store the "Golden Copy" in an immutable, air-gapped environment (e.g., WORM storage).
  • Test the restoration of the "Golden Copy" in a sandbox environment to ensure it is bootable.

Integration Audit

  • Catalog all third-party API integrations (e.g., Stripe, SendGrid, Auth0).
  • Regenerate and secure new API keys for the target environment.
  • Configure SMTP relay settings for transactional emails in the new provider’s dashboard.
  • Audit Webhooks for all incoming traffic; update endpoints to the new provider’s load balancer.
  • Review DNS TTL (Time-to-Live) settings; lower to 60 seconds to prepare for rapid cutover.

Phase 2: Migration Execution

Pre-Cutover

  • Notify stakeholders of the planned maintenance window via official communication channels.
  • Set the existing application to 'Read-Only' mode to prevent data drift.
  • Execute the final delta sync of data from the source to the target environment.
  • Validate that all environment variables are correctly injected into the new containers/VMs.
  • Confirm firewall rules (Security Groups) allow only necessary traffic (ports 80, 443, 22).

Cutover Day

  • Initiate the database migration script and monitor for errors.
  • Update DNS records (A/CNAME/ALIAS) to point to the new provider’s ingress controller.
  • Flush local DNS caches and verify propagation via dig or nslookup.
  • Verify that the SSL/TLS handshake completes successfully on the new endpoint.
  • Monitor CPU/Memory spikes during initial traffic re-routing.

Verification

  • Run automated smoke tests against critical user journeys (Login, Checkout, Profile).
  • Review application logs for 5xx errors or database connection timeouts.
  • Validate that all background workers (Cron jobs, message queues) have started.
  • Confirm that monitoring tools (e.g., Datadog, CloudWatch) are receiving telemetry from the new host.
  • Perform a final sanity check on data consistency between the old and new databases.

Phase 3: Post-Migration Optimization

Stabilization

  • Monitor error rates for 48 hours post-migration.
  • Review auto-scaling policies to ensure they trigger based on the new environment's performance profile.
  • Patch any OS-level vulnerabilities discovered during the initial deployment phase.
  • Update internal documentation and Runbooks to reflect the new architecture.

Cleanup

  • Decommission unused instances in the legacy environment.
  • Securely wipe or cryptographically erase legacy block storage.
  • Revoke access permissions for the legacy provider console.
  • Archive logs from the migration process for audit purposes.

Retrospective

  • Conduct a post-mortem meeting to document "lessons learned."
  • Update the Disaster Recovery (DR) plan with the new infrastructure details.
  • Finalise the migration report for executive sign-off.

UK GDPR Compliance Checklist

  • Update the Data Processing Agreement (DPA) with the new provider.
  • Conduct a Data Protection Impact Assessment (DPIA) for the new infrastructure.
  • Ensure data at rest is encrypted using AES-256 or equivalent.
  • Verify that the new provider allows for "Right to Erasure" (Right to be Forgotten) requests.
  • Confirm that cross-border data transfers comply with UK-EU adequacy decisions.
  • Update the Privacy Policy to reflect the new data hosting location.

Troubleshooting Common Issues

  • DNS Latency: Check for cached records on ISP resolvers; force TTL expiry if necessary.
  • Permission Denied: Verify IAM roles and Service Account permissions on the new cloud platform.
  • Database Mismatch: Check for version differences between source (e.g., MySQL 5.7) and target (e.g., MySQL 8.0).
  • Broken Assets: Ensure S3/Blob storage CORS policies are updated to allow the new domain.

Downloadable Resources List

  • [ ] Migration Risk Assessment Template (Excel/CSV)
  • [ ] Infrastructure Dependency Map Template (Lucidchart/Draw.io)
  • [ ] Post-Migration Sign-off Document (PDF)
  • [ ] UK GDPR Compliance Audit Log (Template)
  • [ ] Troubleshooting Runbook (Confluence/Markdown)