101 The Problem: Legacy Systems PDF

101 The Problem: Legacy Systems ** What are Legacy System? ** Legacy systems are old softwares, technologies, tools, or infrastructures used by an organization. They were often introduced ages ago and might be based on ** outdated technologies, ** but they continu...

101 The Problem: Legacy Systems ** What are Legacy System? ** Legacy systems are old softwares, technologies, tools, or infrastructures used by an organization. They were often introduced ages ago and might be based on ** outdated technologies, ** but they continue to provide ** essential functions, and that's why they've stuck around. ** Challenges with Legacy Systems 1. Technical Debt Over the years, patches, fixes, and new features might have been ** added haphazardly, ** leading to a ** complex, ** ** hard-to-maintain codebase. ** 2. Obsolete Technology The technology stack may no longer be in vogue, making it difficult to find ** experts or ** ** support. ** 3. Integration Issues Modern tools and services ** might not easily integrate with older systems, ~~ ~~ ** causing ** silos of information. ** 4. Scalability Concerns Legacy systems might not be designed to handle **~~ today's scale or might not be ~~** **~~ cloud-ready. ~~** 5. Costly Maintenance As the system ages, maintenance can become more expensive, both in terms of ** time and ** ** resources. ** 6. Security Vulnerabilities Older systems may not have been designed with **~~ current security best practices in mind, making them ~~** ** susceptible to attacks. ** Why is Replacing Legacy Systems Hard? 1. Critical Operations: Many legacy systems are deeply embedded in an organization's ** critical operations. ** Any disruption can have ** significant impacts. ** 2. Migration Risks: Data migration from old to new systems can be fraught with risks like ** data loss or ** ** corruption. ** 3. Training & Adoption: ** Staff might be used to the old system. ** Introducing a new system requires ** training and can ** face ** resistance. ** 4. High Costs: Building a new system and ensuring it works as ** reliably as the old one can be ** ** expensive. ** 5. Unknown Unknowns: There may be ** undocumented features or ** ** behaviors ** in the legacy system that users have come to rely upon. Strangler Fig Pattern to the Rescue: Here is how the strangler fig design pattern helps us replacing the legacy system: 1. Incremental Replacement: Instead of a ~~ big bang approach, ~~ replace the legacy system ** piece by piece. ** This ** reduces risks and allows for ** ** iterative feedback. ** 2. Coexistence: The new and old systems run ** side-by-side. ** As features are moved to the new system, ** traffic is rerouted accordingly, ** ensuring operations continue without ~~ disruption. ~~ 3. Feedback Loops: By ** gradually transitioning users, ** ** feedback can be obtained ** ** early and often. ** This ensures the new system ** meets user needs. ** 3. Reduced Risk: If a part of the new system has ** issues, it's ** ** easier to revert changes or ** ** fix them without affecting the entire system. ~~ ~~** 4. Flexibility: The pattern provides flexibility in ** adopting new technologies. ** As the industry evolves, the ** new system can evolve with it. ** 5. End Goal: Over time, the ** legacy system's functionality is ** ** entirely replaced by the new system. ** Once the old system has ** no more active users ~~ ~~ or features, ~~ ~~** it can be ** safely retired. **