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Migrating Legacy Systems to the Cloud: A Step-by-Step Guide

Eric Torres
15 min read
Migrating Legacy Systems to the Cloud: A Step-by-Step Guide

Follow our proven methodology for transitioning outdated infrastructure to modern cloud solutions. This comprehensive guide covers assessment, planning, execution, and optimization phases with real-world examples from our client projects.

Introduction

Legacy systems present significant challenges for modern businesses: they're expensive to maintain, difficult to scale, and often create security vulnerabilities. Yet, many organizations hesitate to migrate due to perceived complexity and risk. At CoreBytes, we've developed a systematic approach to cloud migration that minimizes disruption while maximizing the benefits of cloud infrastructure.

Phase 1: Assessment and Discovery

Before any migration begins, a thorough assessment is essential to understand the current state and define the target state.

Application Portfolio Analysis

We begin by cataloging all applications, their dependencies, and their business importance. This includes:

  • Identifying all applications and their owners
  • Documenting dependencies between applications
  • Assessing the technical debt of each application
  • Determining the business criticality and usage patterns

Infrastructure Inventory

Next, we create a detailed inventory of all infrastructure components:

  • Servers (physical and virtual)
  • Storage systems
  • Network components
  • Database systems
  • Security controls

Migration Readiness Assessment

We evaluate organizational readiness across several dimensions:

  • Technical capabilities and skills gaps
  • Operational processes and governance
  • Security and compliance requirements
  • Business continuity needs

Phase 2: Strategy and Planning

With a clear understanding of the current state, we develop a comprehensive migration strategy.

Migration Strategy Selection

For each application, we select the appropriate migration strategy:

  • Rehost (Lift and Shift): Moving applications without significant changes
  • Replatform (Lift and Optimize): Making targeted optimizations during migration
  • Refactor/Re-architect: Significantly modifying applications to leverage cloud capabilities
  • Repurchase: Moving to a different product, often SaaS
  • Retire: Eliminating applications that are no longer needed
  • Retain: Keeping applications on-premises (temporarily or permanently)

Cloud Provider Selection

We help clients select the optimal cloud provider(s) based on:

  • Technical requirements and service offerings
  • Geographic availability and data sovereignty needs
  • Cost structure and pricing models
  • Existing relationships and enterprise agreements

Phase 3: Execution

With planning complete, we move to the execution phase, following a wave-based approach.

Foundation Building

We establish the cloud foundation:

  • Setting up cloud accounts and subscription structures
  • Implementing identity and access management
  • Establishing network connectivity (VPNs, Direct Connect, etc.)
  • Configuring security controls and monitoring

Migration Waves

We organize applications into migration waves based on:

  • Dependencies and integration points
  • Business criticality and risk tolerance
  • Technical complexity
  • Business cycles and change windows

Phase 4: Optimization

Migration is just the beginning. After applications are running in the cloud, we focus on optimization:

Performance Optimization

  • Right-sizing resources based on actual usage
  • Implementing auto-scaling for variable workloads
  • Optimizing database performance
  • Implementing caching strategies

Cost Optimization

  • Reserved instance planning
  • Implementing automated shutdown for non-production environments
  • Storage tiering for infrequently accessed data
  • Continuous cost monitoring and optimization

Case Study: Financial Services Migration

One of our clients, a mid-sized financial services company, successfully migrated their core banking platform from on-premises infrastructure to AWS using our methodology. The results included:

  • 40% reduction in infrastructure costs
  • 99.99% availability (up from 99.9%)
  • 75% faster deployment of new features
  • Enhanced security posture with improved threat detection

Conclusion

Cloud migration is a complex undertaking, but with a structured approach, the benefits far outweigh the challenges. Our methodology has been refined through dozens of successful migrations across various industries and technology stacks.

If you're considering migrating your legacy systems to the cloud, we'd be happy to discuss how our approach can be tailored to your specific needs and objectives.

ET

Eric Torres

Cloud Solutions Architect at CoreBytes

Eric has led numerous cloud migration projects for enterprise clients. He specializes in AWS and Azure architectures and has helped organizations across finance, healthcare, and retail sectors modernize their infrastructure.

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