Cloud Migration Rehosting Replatforming and Refactoring

Lecture 36 of SE602 Software Re-Engineering explores enterprise cloud migration frameworks and modernization pathways. Students analyze the industry-standard '6 Rs' cloud migration strategy: Rehosting (Lift and Shift, moving virtualized legacy workloads to cloud infrastructure without modification), Replatforming (Lift, Tinker, and Shift, replacing legacy databases with managed cloud database services), Repurchasing (transitioning to SaaS), Refactoring / Re-architecting (re-engineering software into cloud-native architectures leveraging serverless functions and microservices), Retiring, and Retaining. The lecture details containerization technologies using Docker and Kubernetes, examining how packaging legacy code into containerized micro-units provides operational portability, dynamic elasticity, and high-availability across multi-cloud environments. Legal and ethical constraints surrounding reverse engineering, clean-room design implementations, and software intellectual property rights are reviewed. By engaging with solved past papers by Moaaz and Waqar Siddhu, learners gain actionable insights into recurrent university exam questions. Interactive quiz assessments on VU SIGMA facilitate rapid knowledge verification and retention of critical software re-engineering concepts. Comprehensive coverage of standard academic benchmarks ensures learners communicate with technical precision across software engineering disciplines. Detailed analysis of code smell topologies highlights the imperative of eradicating duplicate logic, long methods, and bloated god classes. Test harness construction including characterization testing and regression suites are contrasted with traditional unit testing strategies. Students evaluate the trade-offs between big-bang system rewrites and progressive evolutionary refactoring in mission-critical environments. The lesson explores cognitive program comprehension models, top-down hypothesis validation, and mental mappings of complex legacy architectures. Practical code illustrations demonstrate safe code transformations, automated refactoring preconditions, and behavioral equivalence preservation. Scholars analyze Chidamber-Kemerer object-oriented metrics including WMC, CBO, and RFC to quantify the architectural impact of refactoring. Cloud migration pathways including rehosting, replatforming, and cloud-native refactoring are examined as extensions of legacy modernization. The relationship between technical debt accumulation, architectural degradation, and long-term enterprise software viability is reinforced. In this lecture, students examine formal methodologies, structural transformations, and analytical metrics of software re-engineering systems. Through detailed theoretical breakdowns, the lesson explores software evolution dynamics, legacy system preservation, and maintainability enhancement.