Case Study: Modernizing a Legacy .NET App to Cloud-Native on AWS

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Meerako — Dallas, TX experts specializing in complex legacy system modernization and AWS cloud migration.

Introduction

A large Dallas-based manufacturing company relied on a mission-critical, internally-developed application built over a decade ago using an older Microsoft .NET Framework and running on aging Windows servers in their on-premise data center.

The application worked, but it was becoming a major liability:

• Slow & Unreliable: Frequent crashes and performance issues.
• Difficult to Update: Deploying new features took weeks and often broke things.
• Expensive to Maintain: Managing the old servers and Windows licenses was costly.
• Security Risks: Running on an unsupported OS version posed significant security threats.

They needed to modernize, but a complete rewrite was deemed too risky and expensive initially. They needed a phased approach to move to the cloud and gradually refactor. They chose Meerako, leveraging our expertise in both legacy systems and modern AWS cloud-native architectures.

What You'll Learn

• The specific challenges of modernizing a legacy .NET monolith.
• Meerako's phased migration strategy (Rehost -> Replatform -> Refactor).
• Leveraging AWS services purpose-built for .NET workloads.
• The measurable benefits: Cost savings, agility, and reliability.

The Challenge: A Fragile .NET Monolith

• Technology: .NET Framework 4.5, ASP.NET Web Forms, WCF services, SQL Server 2008.
• Infrastructure: Physical Windows Server 2008 R2 machines.
• Pain Points: Tightly coupled code, lack of automated testing, manual deployment process, security vulnerabilities.

Meerako's Phased Modernization Strategy

We didn't attempt a "big bang" rewrite. We used a pragmatic, multi-phase approach based on the "6 R's":

Phase 1: Rehost ("Lift and Shift" to EC2)

• Goal: Get the application off the aging on-premise hardware quickly and into a stable AWS environment.
• Action: We used the AWS Application Migration Service (MGN) to replicate the existing Windows Server VMs directly into Amazon EC2 instances running within a secure VPC. The SQL Server database was similarly lifted-and-shifted to an EC2 instance initially.
• Result: Application running on reliable AWS infrastructure within weeks. Immediate reduction in hardware maintenance costs. This bought us time for the next phase.

Phase 2: Replatform (Optimize for AWS Managed Services)

• Goal: Reduce management overhead and improve scalability by moving key components to AWS managed services.
• Action:
  • Database: Migrated the SQL Server database from EC2 to Amazon RDS for SQL Server. This offloaded patching, backups, and scaling to AWS.
  • Containerization (.NET Core): We worked with the client's team to upgrade parts of the application from the old .NET Framework to the modern, cross-platform .NET 7/8. We containerized these components using Docker.
  • Orchestration: Deployed the containerized .NET services onto AWS ECS with Fargate (serverless containers), eliminating the need to manage EC2 instances for the application tier.
• Result: Significant reduction in server management. Improved database reliability. Basic auto-scaling capabilities for the application tier.

Phase 3: Refactor / Re-architect (Ongoing Microservices & Serverless)

• Goal: Gradually break down the monolith into smaller, independent services to improve agility and unlock true cloud-native benefits.
• Action (Ongoing): This is a continuous process. We identify specific domains within the application (e.g., "Inventory Management," "Order Processing") and refactor them into:
  • Microservices: Independent .NET services running on ECS/Fargate or potentially EKS.
  • Serverless Functions: Event-driven logic migrated to AWS Lambda (using .NET runtime).
  • API Gateway: Introduced AWS API Gateway as the front door, decoupling clients from the evolving backend.
• Result: Increased deployment frequency, improved fault isolation, ability to scale specific components independently, adoption of modern DevOps practices.

The Measurable Benefits

Through this phased approach, the Dallas manufacturing company achieved:

• ~40% Reduction in total infrastructure and maintenance costs.
• Improved Application Uptime from ~98% to over 99.95%.
• Faster Feature Deployment: Release cycles reduced from quarterly to bi-weekly sprints.
• Enhanced Security: Running on supported OS versions with robust AWS security controls (CSPM).
• Foundation for Innovation: Enabled integration of new technologies like AI/ML for predictive maintenance.

Conclusion

Modernizing legacy applications is a journey, not a destination. A phased approach, starting with getting stable on the cloud (Rehost/Replatform) and then gradually refactoring towards a cloud-native architecture, is often the most pragmatic and least risky path.

Meerako's expertise in both legacy systems (like .NET) and modern AWS cloud-native patterns allows us to guide enterprises like this Dallas manufacturer through a successful transformation, unlocking agility, reliability, and significant cost savings.

Is your legacy application holding your business back? Let's chart your path to the cloud.

🧠 Meerako — Your Trusted Dallas Technology Partner.

From concept to scale, we deliver world-class SaaS, web, and AI solutions.

📞 Call us at +1 469-336-9968 or 💌 email [email protected] for a free consultation.