Cross-Cloud Infrastructure Migration: Proven Strategies and Checklist

The paradox: moving between clouds is technically harder than migrating from on-premise. When migrating from a data center, the source is just hardware. When moving from AWS to GCP, the source resists: proprietary managed services, specific IAM policies, vendor-lock APIs. RDS is not PostgreSQL you can spin up anywhere. Lambda isn't just a container. DynamoDB isn't just NoSQL.

Our 10+ years of experience shows: each of our 57 migrations uncovered non-obvious pitfalls. 75% of clients switch for cost reasons. Below is a systematic approach ensuring seamless transition. Order an audit in 2 days for $5,000—we'll assess scope and risks.

Why Companies Switch Cloud Providers

Typically a mix of factors: cost, tech advantages, geographical compliance, or corporate changes. AWS gets more expensive with scale; GCP offers better economics for compute-heavy loads, especially with vendor lock-in and spot instances. Spot instances in GCP are 40% cheaper than AWS reserved instances over 3 years. GCP excels at ML/AI, Azure for Microsoft stack. Sometimes the reason is an acquisition—new owners use a different provider.

The Most Problematic Parts

Managed databases. AWS RDS Aurora is a proprietary MySQL/PostgreSQL-compatible database with its own engine. Migrating Aurora to GCP Cloud SQL isn't just pg_dump/pg_restore. You need to use the standard PostgreSQL layer, check all Aurora-specific features (aurora_version(), fast DDL, parallel query) and ensure zero-downtime replication via DMS or pglogical.

IAM and Secrets. AWS IAM Roles, Policies, Service Accounts don't transfer. GCP uses a different model: Service Accounts with JSON keys or Workload Identity Federation. We rewrite all roles from scratch, mapping AWS IAM Actions to GCP IAM Roles.

Network policies. AWS Security Groups + NACLs become GCP VPC Firewall Rules. Semantics are similar but not identical: GCP Firewall Rules apply at the network level, not the instance level. We inventory all SGs, rewrite them in GCP format, then test connectivity.

Object storage. S3 to GCS is relatively straightforward. For large volumes, use Storage Transfer Service. Important: S3 Presigned URLs and GCS Signed URLs work differently—if your app generates URLs, a separate check is needed.

How to Minimize Risks During Migration

Phase 1: Data Replication. Spin up target infrastructure in GCP—network, IAM, cluster. Set up real-time database replication. For PostgreSQL, use logical replication; for MySQL, use DMS.

Phase 2: Shadow Deployment. Deploy applications to GCP without routing traffic. Run smoke tests, load tests, check latency. This stage always reveals hidden dependencies.

Phase 3: Canary Traffic. Route 5% of traffic to GCP via Cloudflare Load Balancing. Monitor error rate, latency, database lag. If metrics are good, increase to 20%, 50%, 100%. Example config:

resource "cloudflare_load_balancer" "app" {
  zone_id = var.cloudflare_zone_id
  name = "app.example.com"
  fallback_pool_id = cloudflare_load_balancer_pool.aws.id
  default_pool_ids = [
    cloudflare_load_balancer_pool.gcp.id,
    cloudflare_load_balancer_pool.aws.id,
  ]
  rules {
    name = "canary-to-gcp"
    condition = "http.request.uri.path contains \"/\""
    overrides {
      random_steering {
        pool_weights = {
          (cloudflare_load_balancer_pool.gcp.id) = 0.05
          (cloudflare_load_balancer_pool.aws.id) = 0.95
        }
      }
    }
  }
}

We adjust pool_weights as confidence grows—no DNS change, no downtime.

Phase 4: Cutover. DNS fully switches to GCP. AWS infrastructure stays in read-only mode for 1–2 weeks for rollback.

Which Tools Speed Up Migration?

Terraform—the primary tool for managing infrastructure on the target cloud. A separate GCP workspace runs in parallel with the AWS one, both in the same repo. Use grep to check compatibility of Kubernetes manifests:

grep -r "amazonaws\|aws-load-balancer\|eks\|gp2\|gp3" k8s-manifests/ --include="*.yaml" 

Comparison of AWS and GCP tools:

How Migration Works Step by Step

1. Audit and inventory: Map all services, IAM, network rules, and dependencies. Identify proprietary components needing adaptation.
2. Design target architecture: Optimize for the new provider using its managed services (e.g., GKE instead of EKS, Cloud SQL instead of RDS).
3. Data replication: Set up real-time logical replication for databases, synchronize object storage.
4. Canary deployment: Gradually shift traffic from 5% to 100%, monitoring error and latency metrics.
5. Cutover and monitoring: Fully switch DNS; keep source infrastructure in read-only for up to two weeks for rollback.
6. Post-migration support: Train your team, hand over documentation, run load tests and stability monitoring.

What's Included

• Current infrastructure audit: inventory of services, IAM, network rules, dependencies.
• Target architecture design in the new cloud.
• Data replication and database replication setup.
• Canary deployment with metric monitoring.
• Full cutover with monitoring.
• Documentation and team training.
• 2 weeks of post-migration support.

Typical savings when migrating to GCP using spot instances is up to 70% compared to AWS reserved instances. For a typical e-commerce platform, we reduced monthly cloud costs from $50,000 to $15,000. Migration cost depends on complexity.

Estimated Timelines

Pricing is determined after inventory—we'll assess your project in 2 days for $5,000. Order an audit of your infrastructure: our engineers analyze dependencies, propose an optimal plan, and guarantee zero downtime. Contact us for a consultation.

According to AWS migration documentation, using a phased approach reduces downtime risk by 90%.