Based on a 2024 Talk: The article is based on a talk given at QCon San Francisco in November 2024, exploring the inevitability of legacy systems in successful companies and the importance of transforming them.

• Talk Goals: Provide actionable insights on modernizing legacy systems to ensure future success.

Understanding Legacy Systems:

• Successful Company Phases: Software systems need to evolve differently in different growth phases. Early systems may not support rapid growth.

• Legacy System Characteristics:

  • Substantial Complexity: Organizational, operational, and cognitive complexity slows engineers and increases costs.
  • Drop in Innovation Velocity: Complexity leads to a decrease in innovation velocity as it takes longer to innovate.
  • Degraded Quality of Experience: Poor user experience indicates a legacy system, impacting business.

Why Do Systems Become Legacy?:

• Bit Rot Theory: Software deteriorates over time due to incremental changes and issues like unused code and lack of documentation.
• Law of Architectural Entropy: Software systems lose integrity as features are added without considering the original architecture.

What Is Technical Renovation?:

• Difference from Refactoring: Refactoring is like organizing a closet, while renovation is a more extensive process that introduces new capabilities and meets future business needs.
• Scenarios Needing Renovation: Drastic business requirement changes, significant architecture evolution, and organic outgrowing of existing systems.

Strategies for Technical Renovation:

• Evolutionary Architecture: A flexible approach that identifies fitness functions, enables continuous delivery and evaluation, and leans into incremental changes.
• Make It Work, Make It Right, Make It Fast: A structured approach to renovation, focusing on making the solution work initially, then making it right and fast.
• Deprecation-Driven Development: Systematically eliminating obsolete technology to maintain healthy software systems and redirect resources.
• Intentional Organization Design: Evaluating and changing organizational structure to facilitate communication and collaboration for renovation.