Quick Summary
This blog explains why AWS to Azure migration projects often fail silently despite appearing straightforward. You get a detailed breakdown of service mapping, dual-running costs, and migration strategies that every CTO needs to make board-ready decisions.
Table of Contents
Introduction
Two clouds. Same workloads. So why do so many AWS to Azure migrations end with a bigger bill, not a smaller one?
The answer is hardly technical, but it’s because AWS and Azure only look like mirror images.
Underneath, identity works differently, networking is built on different assumptions, and the savings everyone promises are locked behind conditions most teams never check.
That gap between expectation and reality is exactly why the global cloud migration services market is projected to grow from $19.28 billion in 2026 to $143.7 billion by 2035. A market that large doesn’t just reflect demand. It reflects how often migrations need fixing, redoing, or rescuing by outside help.
What is AWS to Azure Migration?
AWS to Azure migration is the process of moving workloads, data, applications, and supporting infrastructure off Amazon Web Services and onto Microsoft Azure. That definition is simple; the reality is not. The two clouds reached feature parity on the big primitives years ago, so the question is never can Azure run this, it’s how much has to change to run it well.
Migrate when your organization is already Microsoft-heavy. If you’re running Microsoft 365, Teams, or on-prem Active Directory, Azure integrates natively and cuts licensing costs through bundled agreements, such as MACC or Azure Hybrid Benefit.
Migrate when compliance or data sovereignty demands it. Azure’s regional footprint and built-in compliance certifications (FedRAMP, HIPAA, ISO 27001) often have an edge for regulated industries, especially in regions where Microsoft has longer-standing government contracts.
Migrate when AWS costs are spiraling, and Azure offers a negotiated deal. Large enterprises often get significant discounts through existing Microsoft EAs (Enterprise Agreements), making a migration financially worthwhile even after accounting for transition costs.
Those signals point to the deeper drivers that hold up under scrutiny:
- An existing Microsoft estate: Organizations standardized on Microsoft 365, Windows Server, and SQL Server gain operational and licensing leverage by consolidating onto Azure.
- License mobility: Azure Hybrid Benefit lets you reuse existing Windows and SQL Server licenses, which is where the real savings live for the right workloads.
- Azure OpenAI and AI services: Teams building on Azure’s AI stack often want their data and compute on the same platform.
- Vendor consolidation: Fewer contracts, one identity plane, and unified governance across the Microsoft ecosystem.
It does not hold up because Azure looks cheaper. For a Linux-heavy, open-source stack with no Microsoft licensing to bring across, the cost case is often neutral. A migration should be driven by a strategic reason you can defend to the board, not by a pricing-page comparison.
If your reason is on the list above, the move is worth scoping. If it isn’t, model the numbers hard before committing.
Still Evaluating AWS vs Azure for Your Enterprise Stack?
Opt for Azure consulting services from Bacancy to assess licensing benefits, architecture fit, and real migration ROI before committing.
AWS to Azure Service Mapping: AWS Services and Their Azure Equivalents
Most AWS services have a clear Azure equivalent on paper, but the Migration note column below is where the actual work lives. Compute and storage map cleanly; identity, networking, and infrastructure-as-code need genuine rework.
| AWS Service | Azure Equivalent
| Migration Note
|
|---|
| EC2
| Virtual Machines
| Closest 1:1 mapping. Instance families and disk types differ; right-size on assessment data.
|
| S3
| Blob Storage
| Direct equivalent. Access models and bucket policies differ; ACLs do not port over
|
| RDS | Azure SQL Database / Azure Database for PostgreSQL / MySQL | Engine-dependent. SQL Server moves cleanly; Aurora has no direct equal and needs replatforming.
|
| Lambda
| Azure Functions
| Similar model, different triggers and runtimes. Event wiring is rebuilt.
|
| EKS
| AKS | Both managed Kubernetes. Manifests port; networking, ingress, and identity bindings.
|
| ECS | Container Apps / Container Instances / AKS
| No single equivalent. Choice depends on the orchestration model you want.
|
| VPC | Virtual Network (VNet)
| Conceptually similar, structurally different. Subnets, route tables, and security groups need redesign.
|
| IAM | Microsoft Entra ID
| Not a 1:1 mapping. Roles, policies, and trust relationships are re-modeled.
|
| CloudFormation
| ARM templates / Bicep
| Full rewrite. No converter produces production-ready output.
|
| CloudWatch
| Azure Monitor
| Different metrics, logs, and alerting. Dashboards and alarms were rebuilt from scratch.
|
| DynamoDB
| Cosmos DB
| Both NoSQL, different APIs, and consistency models. Data-access code changes.
|
| Route 53
| Azure DNS
| Direct DNS equivalent. Health-check and routing-policy features differ.
|
| SNS / SQS
| Service Bus / Event Grid / Queue Storage
| One AWS service splits into several Azure services by messaging pattern.
|
Networking and Identity Differences Between AWS and Azure
AWS and Azure handle networking and identity differently. AWS uses VPCs, subnets, security groups, and IAM for access control, while Azure relies on VNets, NSGs, and Azure Active Directory for identity and permissions. differences affect resource connectivity, authentication, and policy enforcement, making direct migration between clouds non-trivial.
On networking, an AWS VPC and an Azure VNet both isolate workloads. AWS security groups are stateful, instance-level firewalls, and Azure uses Network Security Groups attached to subnets or interfaces with different rules, precedence and evaluation.
On identity, the gap is wider and more dangerous. AWS IAM is a policy engine attached to resources. Microsoft Entra ID is a directory service that handles users, groups, and roles through role-based access control. Mapping IAM roles and policies onto Entra ID is the single most underestimated task in most migrations, because no tool translates one into the other safely.
It is manual, security-sensitive work, and getting it wrong means either locked-out services or over-permissioned access that fails an audit.
The rule for a CTO: neither networking nor identity is a 1:1 translation, so fund and plan them first, not as cutover-week cleanup.
How Much Does an AWS to Azure Migration Cost?
An AWS to Azure migration typically costs between $10,000 and $1M+, depending on workload size and complexity. Small workloads with few dependencies run roughly $10k-$50k, mid-sized applications $50k-$200k, and large enterprise migrations with refactoring and compliance needs $300k-$1M+.
For context, a full-scale enterprise migration of 50 or more applications averages around $1.2 million and roughly eight months. Costs cover planning, data transfer, refactoring, testing, downtime management, and post-migration optimization.
- Data egress, and an important 2026 update. AWS historically charged around $0.09 per GB to move data out to the internet, which made large migrations expensive on transfer alone. That advice is now largely outdated. As of 2025 and 2026, AWS waives egress fees for customers migrating data off the platform, typically through 60-to-90-day migration credits. Coordinate the move with AWS, and this cost can approach zero; run an uncoordinated transfer, and you still pay standard rates.
- Dual-running. During cutover, you pay for both clouds at once. The longer the parallel period, the higher the overlap, which is why a tested, time-boxed cutover is a cost control as much as a risk control.
- License mobility. This is where Azure’s real savings live. If you already hold Windows Server or SQL Server licenses with Software Assurance, Azure Hybrid Benefit can reduce costs by up to 85% over pay-as-you-go when combined with reserved instances, and it grants a 180-day window to run workloads on both clouds during migration. Without those licenses, that advantage disappears, and the cost case is often neutral.
- The CTO takeaway: savings depend on your stack. Model dual-running, license mobility, and coordinated data transfer before you commit, rather than trusting a generic Azure is a cheaper claim. Bacancy’s cloud migration services include a pre-migration TCO assessment built for exactly this decision.
AWS to Azure Migration Strategies: The 6 R's
Every workload should be sorted into one of the “6 R’s,” and the choice is a deliberate tradeoff between speed, cost, and long-term value. Most projects use a mix rather than one strategy across the board.
- Rehost (lift and shift): Move VMs as-is to Azure Virtual Machines. Fastest and cheapest to execute, but you inherit existing inefficiency and miss Azure-native savings.
- Replatform: Swap a managed service during the move, such as RDS to Azure SQL Database. Modest effort, real operational gains, no full rewrite.
- Refactor: Redesign the app around Azure-native services. Highest upfront cost and risk, highest long-term payoff. Justified for strategic apps held back by their AWS architecture.
- Repurchase: Replace a self-managed component with a SaaS or Azure Marketplace equivalent.
- Retire: Decommission what nobody uses. A migration is an excellent audit moment.
- Retain: Deliberately keep a workload on AWS for now, accepting a multi-cloud posture.
A pragmatic sequence for most organizations is to rehost first to hit the exit deadline, then replatform or refactor the workloads that justify deeper investment once they are stable on Azure. The execution depends on having both sides of the skill set: teams often hire AWS developers who understand the source environment alongside the engineers they hire Azure developers from to own the target design.
Step-by-Step AWS to Azure Migration Process
A reliable AWS to Azure migration follows 8 sequential steps across four phases, with a tested rollback before every cutover. Skipping the early steps is the most common reason migrations run over budget.
Step 1: Inventory your AWS environment
List every server, database, application, and dependency. Map what connects to what, so you migrate complete units rather than orphaned pieces.
Step 2: Run an assessment with Azure Migrate
Use discovery and dependency mapping to right-size targets based on real utilization, and produce a cost and timeline estimate grounded in data, not guesswork.
Step 3: Assign each workload a migration strategy
Sort every workload into one of the 6 R’s (rehost, replatform, refactor, repurchase, retire, retain) based on its cost, risk, and value.
Step 4: Design the target Azure environment
Build the Virtual Network topology and the Microsoft Entra ID identity model up front, since neither carries over from AWS VPC or IAM.
Step 5: Sequence the migration into waves
Order workloads lowest-risk first. Move non-critical workloads ahead of customer-facing ones, and define the rollback procedure for each wave before it runs.
Step 6: Replicate and validate.
Replicate workloads to Azure, then check data integrity, confirm application functionality, and run performance tests against your AWS baseline before committing.
Step 7: Execute a time-boxed cutover
Switch traffic during a low-traffic window. Validate first, cut over second, and trigger the rollback if validation fails. The commit is final.
Step 8: Optimize post-migration
Apply Azure Hybrid Benefit and reserved instances, right-size against actual Azure usage, and rebuild monitoring baselines in Azure Monitor. Treat this as ongoing.
For a working version you can hand your team, Bacancy maintains an Azure migration checklist.
Best Tools for Migration from AWS to Azure
The primary tooling for an AWS to Azure migration lives on the Azure side; the AWS-side tool only tracks what’s leaving. Knowing which tool owns which job avoids wasted setup.
- Azure Migrate: The central hub for discovery, dependency mapping, cost assessment, and server replication. It treats AWS EC2 instances as physical servers and replicates them to Azure VMs through a replication appliance. This is the workhorse for most projects.
- Azure Database Migration Service: Purpose-built for moving databases (SQL Server, PostgreSQL, MySQL) with minimal downtime.
- Azure Data Box: For very large datasets where physical shipping beats network transfer.
- AWS Migration Hub: Useful on the AWS side for tracking what’s migrating out, but it does not move workloads into Azure. Treat it as a source-side inventory aid, not a migration engine.
If you also run AWS infrastructure long term, Bacancy’s AWS migration services cover the source side of the move.
Common AWS to Azure Migration Challenges and How to Avoid Them
Most failed migrations fail on planning gaps, not technology limits. The recurring patterns and their fixes:
- Identity left too late. Teams that defer IAM-to-Entra mapping until cutover week find it cannot be rushed. Re-model it during planning.
- No rollback plan. A cutover without a tested rollback is a bet. Define the rollback per wave before moving it.
- Skipped dependency mapping. Migrating an app without its dependencies produces a workload that starts but doesn’t work. Map first.
- Assuming the savings. Running the move without modeling license mobility and dual-running is how a project ends up costing more than the AWS bill it was meant to cut.
- Lifting inefficiency across. Rehosting an over-provisioned estate as-is just moves the waste to a new invoice. Right-size during optimization.
The single fix behind all five is to front-load assessment and planning. The teams that spend more time before the first workload moves spend far less time firefighting after it.
Post-Migration Checklist to Ensure a Successful Migration from AWS to Azure
Use this checklist to stabilize operations and decide early if ongoing management stays in-house or moves to an Azure managed services partner.
- Validate data integrity against the source, with row counts and checksums, not spot checks.
- Confirm performance meets or beats the AWS baseline you recorded pre-migration.
- Apply Azure Hybrid Benefit and reservations so the license savings actually land on the bill.
- Right-size resources against Azure usage rather than the instance sizes you carried over.
- Rebuild monitoring and alerting in Azure Monitor, including dashboards and on-call routing.
- Verify identity and access in Microsoft Entra ID, checking for over-permissioned roles before they fail an audit.
- Decommission AWS resources only after a defined soak period to confirm Azure is stable.
- Reconcile costs at the first full billing cycle to confirm the projected savings are real.
Bacancy Assists You in Migrating AWS to Azure
We help CTOs plan and execute the move end-to-end, from dependency mapping and TCO analysis through cutover and post-migration optimization. Our certified engineers handle the parts that break most migrations: re-modeling IAM into Microsoft Entra ID, redesigning networking, and sequencing waves so production keeps running throughout.
We worked through exactly this for a financial services client in our AWS to Azure migration for a secure financial platform, modernizing infrastructure with near-zero downtime.
If you’re evaluating a move off AWS, the right starting point is an assessment, not a tooling decision. Our Azure migration services and Azure consulting services teams can scope your estate, model the real cost, and give you a phased plan you can take to the board. Get in touch to start with a migration assessment.
Frequently Asked Questions (FAQs)
Yes, and for most migrations, you should. A wave-based approach keeps production on AWS while you validate workloads on Azure, and Azure Hybrid Benefit grants a 180-day window to run licensed Windows and SQL workloads on both clouds during the transition. Keep the parallel period as short as validation allows, since you pay for both environments while it runs.
Yes. An Azure to AWS migration reverses the direction and the mapping, but the hard parts swap rather than disappear: you would re-model Entra ID into IAM and redesign VNets into VPCs. The same principle applies in both directions, which is that identity and networking carry the work.
Reserved Instances and Savings Plans are tied to AWS and do not transfer to Azure. If you migrate before a term ends, you either keep paying for unused capacity or sell eligible reservations in the AWS marketplace. Time the migration against reservation expiry to avoid paying twice.
Yes, but different from Windows. It covers Red Hat Enterprise Linux and SUSE Linux Enterprise Server subscriptions, with savings that can reach the mid-70s percent versus pay-as-you-go for eligible workloads. It does not apply to community Linux distributions with no paid subscription.
A single rehosted workload can move in days. A multi-service migration with database changes and identity redesign typically runs 3 to 9 months, depending on how many workloads need refactoring and how much can move as a straight rehost. The assessment phase is what produces a reliable timeline.
