Why Cloud Migrations Fail: 7 Lessons from Projects That Went Over Budget
When McKinsey surveyed roughly 450 CIOs and IT leaders, it found migration programs ran an average of 14% over planned spend, and 38% of companies had seen migrations delayed by more than a quarter. Across the market, McKinsey estimated more than $100 billion in wasted migration spend over three years. The numbers have hardly improved since. In CloudBees’ 2025 DevOps Migration Index, more than 300 enterprise technology leaders reported an average cost overrun of 18% on platform migrations and an average loss of $315,000 per project. Very little of that is caused by the cloud providers. It comes from planning decisions made months before the first server moves, which is why Crunch-IS is a leader in cloud migration services: its projects start with dependency mapping and a cost model, not with a migration tool. These are the seven lessons the overruns keep teaching.
1. Budget for two environments, not one
Most migration budgets price the target state: cloud instances, storage, the migration partner. They leave out the cost of running both worlds at once:
- data center leases, power and cooling until the last rack is empty;
- software licenses paid on-premises and again in the cloud;
- support contracts for hardware that is being retired;
- staff time split between keeping the old estate alive and building the new one.
The longer the migration runs, the longer you pay twice. A delay is never only a scheduling problem.
2. Map dependencies before you schedule waves
The application inventory is almost always wrong. A reporting job nobody documented reads from a database scheduled to move in wave two. An authentication service has an internal IP address hardcoded into its config. Each discovery stops a wave while the team investigates, and this is where quarter-long delays come from. Discovery tools that watch real network traffic for several weeks find connections that spreadsheets and stakeholder interviews miss. A few weeks of discovery is cheap next to a stalled wave with a full migration team on the clock.
3. Don’t copy over-provisioned servers into the cloud
On-premises servers are sized for peak load plus headroom, because adding hardware takes months. Copy those sizes into the cloud and the headroom turns into a recurring charge. Flexera’s 2026 State of the Cloud report estimated that 29% of cloud spend is wasted, up from 27% a year earlier. Right-size from measured utilization, not from the old spec sheet. When a deadline forces a workload to move as-is, put it on a list for a second pass within the first quarter after cutover, and give that list an owner.
4. Put security and compliance in the first phase, not the last
In Ekco’s 2024 Infrastructure Modernisation Survey, 79% of respondents said they were worried about the security of their cloud infrastructure. That worry gets expensive when it surfaces late. Identity models, network segmentation, encryption key management and audit logging all shape the target architecture. A compliance review held a week before cutover can force a redesign of environments that are already built and running, and that redesign is billed at cloud rates while the old data center is still switched on.
5. Be honest about the skills gap
A 2025 Ekco survey of more than 1,000 IT decision-makers found that only 27% believed they had the in-house skills to scale the cloud effectively. Teams learning Kubernetes, infrastructure-as-code and cloud networking during a live migration make slow, cautious decisions, and some of them are wrong. The human cost is real too: 70% of respondents in the CloudBees index said their developers burned out during platform migrations, and 61% reported delays of six months or more. Training before the project starts, or bringing in people who have done it before, is cheaper than learning in production.
6. Give cloud costs an owner on day one
A data center bill is fixed. A cloud bill moves every hour. Flexera’s 2025 survey of more than 750 technology leaders found cloud budgets running 17% over their limits, and 84% called managing cloud spend their top challenge; 59% said they were expanding FinOps teams in response. Overruns persist where nobody owns them. Tag every resource to a team and a budget from the first workload, set alerts, and review spend weekly during the migration rather than quarterly after it.
7. Define success as an outcome, not a server count
“Migrated 400 servers” is an activity report. Ekco found that only 32% of cloud projects met all their objectives, and 66% of respondents who had just finished one had made cost compromises along the way. CloudBees reported that 94% of organizations saw slower or similar system performance after migration. If the goal was faster releases, lower unit cost or better resilience, measure it before the migration starts, so there is a baseline to prove it improved.
What the over-budget projects have in common
Line the survey findings up and the cloud provider rarely appears as the cause. The overruns trace back to an incomplete inventory, a budget that ignored the overlap period, a team learning on the job, and a bill nobody owned after go-live. Every one of those is a decision made before migration day, and every one is cheaper to fix on paper than in production.
