Architecting Large-Scale AWS Migrations Using AWS Application Migration Service (MGN) & Cloud Studio 2.0

Introduction
Cloud migration often looks simple on paper, “lift and shift the servers and run them on AWS.”
But architects know the reality is dramatically different.
Enterprise migrations involve multi-tier apps, interdependent services, legacy systems, compliance requirements, weekend cutovers, and the never-ending question “Will the application work exactly the same after cutover?”

AWS Application Migration Service (MGN) significantly simplifies rehosting, yet the architecture behind a scalable migration is where most projects struggle.

In this blog, I will walk through how to architect large migrations using AWS MGN, combined with Cloud Studio 2.0, an accelerator that helps automate discovery, dependency mapping, and migration wave planning (Cloud Studio is a Wipro’s proprietary tool/ Platform, Instead of Cloud Studio tool you can use other third-party tools as well based on your requirement and use case, example Matilda etc.). These approaches come from real-world programs supporting enterprise customers transitioning hundreds of servers to AWS.

1. Migration Strategy: Why Rehost Still Matters
The industry loves buzzwords - containers, serverless, AI-driven modernization, but most enterprises still choose rehost as the first step toward modernization.

Reasons:
• Quickest path to cloud
• Minimal code changes
• Lower risk for legacy systems
• Easier to validate and rollback

MGN is the AWS-native service that supports rehosting at scale with:
• Continuous block-level replication
• Automated cutover
• Minimal downtime
• Integrated testing workflows

For large enterprises with heavy operational workloads, MGN becomes the backbone of the migration engine.

2. AWS MGN Architecture Deep Dive
An effective migration architecture with MGN typically includes:

Key Components
• Source Servers - On-prem, VMware, Hyper-V, bare metal
• Replication Agent - Installed on each source server
• Staging Area - Lightweight EC2 instances + EBS volumes
• Replication Server - Temporary instance managing data sync
• Test & Cutover Instances - Automatically created based on launch templates

Why This Architecture Works
• Real-time replication
• Ability to perform functional and performance tests
• Supports rollback without data loss
• Handles heterogeneous environments (Linux/Windows/x86/ARM)

Common Architectural Decisions
• Placement of staging area subnets
• Choosing instance types for test/cutover
• IAM boundaries for migration teams
• Cross-account replication for regulated workloads

3. Discovery & Migration Planning With Cloud Studio 2.0
One of the biggest challenges in migrating 100+ servers is understanding:
• Which servers talk to which
• Which app depends on what
• Which servers can move together
• How much downtime is tolerable

Cloud Studio 2.0 solves these by offering:

Key Capabilities

1. Automated Discovery Application topology, ports, dependencies, network flows.
2. Dependency Mapping Identifies upstream/downstream services.

3. Wave Planning
   Groups servers into migration waves automatically.

4. Effort Estimation
   Provides migration timelines, resource needs, and cutover planning.

5. Runbooks
   Generates standardized migration steps for each application.
   This combination- Cloud Studio for planning, MGN for execution - dramatically reduces migration time.

4. Reference Migration Architecture

Reference – Amazon user-guide.

5. Best Practices for Enterprise-Scale Migration

1. Warm-Up Replications Early Start replication weeks before cutover to: • Stabilize data sync • Detect slow links or IO bottlenecks
2. Create Separate Accounts for Migration • One for staging • One for production • One for dev/testing
3. Standardize Launch Templates Avoid manual configurations.
4. Run Multiple Test Cycles Functional testing + performance testing.
5. Use MGN Post-Cutover Actions Automate • Agent removal • Disk cleanup • Domain joining • Security patching

*6. Real World Example *
A global retailer needed to migrate 115 servers across 23 applications.

Challenges:
• Unknown dependencies
• Strict weekend downtime
• Heavy data sync volumes

Solution:
• Cloud Studio 2.0 → Dependency mapping & wave planning
• MGN → Continuous replication & automated cutover
• Systems Manager → Post-migration automation

Outcome:
• Zero rollback occurrences
• 60% reduction in migration planning effort
• Smooth cutover within the approved downtime window

Conclusion
Large-scale migrations require more than a tool, they need an architecture-firstmindset, strong planning, and reliable automation. AWS MGN paired with CloudStudio2.0 offers a repeatable, scalable, low-risk migration framework.

Whether you're rehosting 10 servers or 1,000, the architecture described above provides a solid blueprint to deliver predictable results.