Cloud migration promises lower costs, faster scaling, and infrastructure that finally works at the speed of your business. Most IT leaders sign up for all three. Not all of them get what they paid for.
The numbers are blunt. According to IDC, 38% of migrations exceed their original budget, with the average overrun running 23% above plan. Meanwhile, the Flexera 2026 State of the Cloud Report found that 29% of all cloud spend is wasted, a figure that ticked upward for the first time in five years, driven largely by the complexity introduced by AI and new cloud services.
The problem is rarely the cloud itself. It is how organizations approach the migration: without a readiness assessment, without a governance model, without a tested recovery plan. This article covers five of the most common, and expensive, cloud migration mistakes businesses make, and what to do instead.
1. Skipping a Cloud Readiness Assessment
The most expensive phase of a cloud migration is the one most organizations skip entirely: the assessment. Moving workloads without first understanding your application dependencies, data volumes, compliance requirements, and true total cost of ownership is the primary reason migrations blow budgets and timelines.
The data bears this out. IDC research shows that 31% of migrations miss their planned timeline, with the complexity of legacy applications cited as the number one cause. Organizations that conduct a formal readiness assessment before migrating have 2.4x higher success rates than those that do not. Despite this, 59% of organizations reported that poor planning was the primary cause of delays in their cloud go-live process.
“Diving into a cloud migration without watertight planning and a concrete strategy is the foremost mistake businesses make. This leads to unforeseen costs, delays, and failures.” — EpiUse, 2025
To avoid becoming part of that statistic:
- Map your application dependencies before you migrate anything. Moving a workload without understanding what it talks to is the fastest way to break production.
- Conduct a TCO analysis that accounts for licensing, data egress fees, training, and managed services — not just compute and storage costs.
- Score each workload for cloud readiness. Not every application benefits from a lift-and-shift. Some require refactoring; others belong on-premises.
- Define your RTO and RPO requirements upfront. Recovery time and data loss tolerances shape architecture decisions — they cannot be retrofitted after the fact.
2. Underestimating Cloud Cost Management
Once in the cloud, the expectation is that costs go down. For many organizations, the opposite happens — at least initially. Cloud environments create new categories of spend: idle resources left running, oversized instances provisioned for peak loads that never arrive, and orphaned snapshots quietly accumulating charges.
The Flexera 2025 State of the Cloud Report — based on a survey of more than 750 cloud decision-makers — found that 84% of organizations cite managing cloud spend as their top cloud challenge. Cloud budgets were already exceeding limits by 17%, and cloud spend was projected to grow by another 28% in the coming year. The Flexera 2026 Report confirmed the trend: wasted spend ticked back up to 29% of IaaS and PaaS budgets after five years of improvement.
| Cloud Cost Management Stat | Source |
|---|---|
| 84% cite managing cloud spend as top challenge | Flexera 2025 State of the Cloud |
| 29% of IaaS/PaaS spend is wasted | Flexera 2026 State of the Cloud |
| Cloud budgets exceeded limits by 17% on average | Flexera 2025 State of the Cloud |
| 38% of migrations exceeded original budget | IDC, via Medha Cloud 2026 |
To get real control over cloud costs:
- Implement a FinOps practice. Engineering, finance, and operations managing cloud costs jointly is the foundation of cost discipline at scale.
- Right-size your instances before committing to reserved capacity.
- Use auto-scaling and resource cleanup automation to eliminate idle and orphaned resources automatically.
- Leverage committed-use discounts and reserved instances for predictable workloads, still underutilized by more than half of organizations.
3. Treating Security as an Afterthought
Gartner has projected that 99% of cloud security failures will be the customer’s fault, primarily due to misconfigurations. The 2025 CrowdStrike Global Threat Report found that cloud-conscious intrusions jumped 37% year-over-year in 2025, and 80% of organizations experienced a cloud breach in the past year.
During migration, security gaps multiply. Permissions get set too broadly, storage buckets are left publicly accessible, encryption is skipped to hit a go-live deadline. According to IBM’s 2024 Cost of a Data Breach Report, 40% of breaches involved data distributed across multiple environments, exactly the scenario created by a hybrid migration that is not properly governed. Breaches involving only public cloud systems averaged $5.17 million per incident.
To avoid turning your migration into a security event:
- Apply the principle of least privilege from day one. Every account, service identity, and API key should have exactly the permissions it needs, nothing more.
- Audit IAM configurations before and after migration. Overprivileged accounts are the most common vector for lateral movement.
- Enable logging and monitoring immediately — AWS CloudTrail, Azure Monitor, Google Cloud Audit Logs, from the first workload.
- Run a post-migration security review against the Cloud Security Alliance Top Threats.
4. Migrating Without a Tested Disaster Recovery Plan
Between August 2024 and August 2025, the three largest cloud platforms experienced more than 100 service disruptions. Unplanned downtime averaged $14,000 to $23,750 per minute depending on company size, according to New Relic’s 2025 Observability Forecast. The ITIC 2024 Hourly Cost of Downtime Survey found that 90% of mid-sized and large enterprises lose upwards of $300,000 per hour of downtime, with 41% reporting losses between $1 million and $5 million per hour.
The risk compounds when ransomware is involved. Sophos found ransomware hit 59% of organizations in 2024. Fewer than 7% recovered within a day; more than a third took longer than a month.
To build disaster recovery that actually works in the cloud:
- Define RTO and RPO before choosing a DR architecture. Recovery objectives are business decisions that set technical requirements, not the other way around.
- Test your failover quarterly, not annually. Untested DR plans fail at a substantially higher rate when invoked under real conditions.
- Use cloud-native DRaaS solutions with automated failover and multi-region redundancy.
- Follow the 3-2-1 backup rule: three copies, two types of media, one isolated from your production network.
5. Ignoring Application Dependency and Legacy Technical Debt
IDC data shows that 41% of organizations experience performance degradation for legacy applications after moving them to the cloud. 30% of applications require significant code refactoring that was never planned for. And 56% of cloud migrations encounter unforeseen technical debt that prevents full realization of expected benefits.
The consequences are financial as well as technical. Organizations that rush migrations without resolving technical debt often pay for two environments simultaneously: the new cloud footprint and the on-premises systems they cannot yet retire.
- Run application dependency mapping before migration planning using tools like Azure Migrate or AWS Application Discovery Service.
- Categorize workloads by migration strategy (the six Rs: Rehost, Replatform, Repurchase, Refactor, Retire, Retain).
- Resolve data quality issues before migration, not after. 35% of migration projects fail due to poor data quality discovered only post-move.
- Invest in a hypercare period — 30 to 90 days of intensive monitoring immediately after each workload cutover.
In Summary
The five cloud migration mistakes share a common thread: they feel like shortcuts in the short term and become expensive problems in the long term. None require unlimited budgets to fix. All require deliberate action before migration begins, not after.
For many businesses, particularly those without a dedicated cloud team, partnering with a managed services provider is the most efficient way to close all five gaps simultaneously. MSPs bring migration expertise, FinOps tooling, security posture management, and ongoing infrastructure support that are difficult and expensive to build internally.
