5 Critical Mistakes to Avoid During Cloud Migration

After migrating over 500 enterprise workloads to AWS, Azure, and Google Cloud, we've seen patterns emerge in both successful and failed migrations. This article shares the five most critical mistakes we've observed and how to avoid them, based on real-world experience and lessons learned the hard way.

Mistake #1: Lift-and-Shift Without Optimization

The Problem

The most common mistake is treating cloud migration as a simple datacenter relocation—moving applications "as-is" without leveraging cloud-native capabilities. While AWS's migration strategies include "rehost" (lift-and-shift) as a valid approach, stopping there leaves significant value on the table.

Common Symptoms:

• Cloud costs exceed on-premises costs
• Performance doesn't improve (or degrades)
• Unable to leverage auto-scaling or high availability
• Persistent management overhead similar to legacy environment

The Solution

Adopt the 6 R's migration framework from AWS and Microsoft's Cloud Adoption Framework:

• Rehost: Quick migration for time-sensitive workloads
• Replatform: Minimal optimization (managed databases, containers)
• Repurchase: Move to SaaS alternatives
• Refactor: Re-architect for cloud-native benefits
• Retire: Decommission unused applications
• Retain: Keep on-premises when appropriate

Best Practice: Start with rehost for quick wins, but plan optimization sprints to refactor high-value applications within 6-12 months post-migration.

Mistake #2: Inadequate Cost Planning and Governance

The Problem

Cloud's pay-as-you-go model provides flexibility but can lead to "bill shock" without proper governance. According to Flexera's State of the Cloud Report, organizations waste an average of 32% of their cloud spend.

Cost Pitfalls:

• Over-provisioned resources never right-sized
• Forgotten dev/test environments running 24/7
• Unattached storage volumes and snapshots
• Data egress charges not factored into design
• Lack of Reserved Instances or Savings Plans

The Solution

Implement comprehensive cost management from day one:

Pre-Migration:

• Use AWS TCO Calculator or Azure TCO Calculator for realistic projections
• Model different instance types and commitment options
• Plan for data transfer and backup costs
• Set budgets and alerts before migration

Post-Migration:

• Deploy cost monitoring tools: CloudZero, Cloudability, or native tools
• Implement tagging strategies for cost allocation
• Schedule regular FinOps reviews
• Use auto-scaling and instance scheduling
• Purchase Reserved Instances or Savings Plans for predictable workloads

Mistake #3: Neglecting Security and Compliance

The Problem

The cloud's shared responsibility model confuses many organizations. While cloud providers secure the infrastructure, you're responsible for securing what you put in the cloud.

Security Gaps We've Seen:

• Publicly accessible S3 buckets or storage accounts
• Overly permissive security groups/NSGs
• Weak IAM policies with excessive permissions
• Missing encryption at rest and in transit
• No logging or monitoring enabled
• Failure to meet regulatory requirements (HIPAA, PCI-DSS, SOC 2)

The Solution

Build security into your migration from the start:

Identity and Access Management:

• Implement least privilege access with AWS IAM or Azure AD
• Enable MFA for all users
• Use service accounts and roles, not long-lived credentials
• Implement just-in-time access

Network Security:

• Design proper VPC/VNet segmentation
• Deploy network firewalls and WAF
• Use private endpoints for PaaS services
• Implement DDoS protection

Data Protection:

• Encrypt all data at rest (AWS KMS, Azure Key Vault)
• Enforce TLS/HTTPS for data in transit
• Classify data and apply appropriate controls
• Implement backup and disaster recovery

Compliance and Governance:

• Use AWS Config, Azure Policy, or Google Cloud Security Command Center
• Enable CloudTrail/Activity Logs for audit trails
• Deploy CSPM tools like Prisma Cloud or Wiz

Mistake #4: Poor Network Architecture and Connectivity

The Problem

Underestimating networking complexity leads to performance issues, security gaps, and connectivity problems. Many organizations discover latency issues or bandwidth constraints only after migration.

Network Challenges:

• Inadequate bandwidth between on-premises and cloud
• High latency affecting application performance
• Complex hybrid connectivity requirements
• Inter-region data transfer costs
• DNS and routing misconfigurations

The Solution

Design proper hybrid cloud connectivity:

Dedicated Connectivity:

• AWS Direct Connect, Azure ExpressRoute, or Google Cloud Interconnect
• Redundant connections for high availability
• Right-size bandwidth based on workload requirements

Architecture Best Practices:

• Use transit gateways for hub-and-spoke topology
• Implement DNS resolution between environments
• Plan IP address space to avoid conflicts
• Consider multi-region architecture for DR

Performance Optimization:

• Deploy applications close to users (Edge locations, CDN)
• Use cloud-native load balancing
• Optimize database queries and caching
• Leverage CloudFront or Azure CDN

Mistake #5: Insufficient Testing and No Rollback Plan

The Problem

Rushing migration without adequate testing or contingency planning creates risk. We've seen migrations where critical issues weren't discovered until production cutover, with no way to quickly rollback.

Testing Gaps:

• Skipping application compatibility testing
• No performance baseline or comparison
• Inadequate user acceptance testing (UAT)
• Disaster recovery not validated
• No rollback procedures documented or tested

The Solution

Implement comprehensive testing and migration safeguards:

Pre-Migration Testing:

• Application discovery and dependency mapping using AWS Application Discovery Service or Azure Migrate
• Proof of concept (POC) for critical applications
• Performance testing in non-production environment
• Security scanning and penetration testing

Migration Execution:

• Phased approach with pilot groups
• Parallel running during cutover period
• Documented runbooks for each application
• Clear success criteria and validation checkpoints
• Communication plan for stakeholders

Contingency Planning:

• Document rollback procedures for each phase
• Maintain on-premises systems until validation complete
• Test DR failback capabilities
• 24/7 support during cutover windows

Additional Considerations

Skills and Training

Invest in cloud training for your team. Leverage AWS Training, Microsoft Learn, and Google Cloud Skills Boost for certification programs.

Automation and IaC

Use Infrastructure as Code from the start with Terraform, AWS CloudFormation, or Azure Bicep to ensure consistency and repeatability.

Change Management

Don't underestimate the people aspect—communicate early and often, provide training, and address concerns about job changes.

Conclusion

Cloud migration is a journey, not a destination. By avoiding these five critical mistakes, you significantly increase the likelihood of a successful migration that delivers real business value. Take time to plan properly, invest in the right tools and training, and don't rush the process.

Remember: the cloud providers want you to succeed—leverage their migration programs, reference architectures, and professional services when needed.