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QCon Beijing - April 2010


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QCon Beijing - April 2010

  1. 1. TECHNICAL DEBT ... And What to Do About It!
  2. 2. THE SPEAKER Kane Mar, Scrum Training Scrum Coaching
  3. 3. DO YOU KNOW THESE PROBLEMS? Your team cannot change the system quick enough to meet changing business needs Your code is so complex only a few people in the company are allowed to make changes Your spend more time fixing defects introduced by new functionality You have recently re-platformed to newer technology
  4. 4. WHY SHOULD YOU CARE? Be able to meet changing business needs Reduce Total Cost of Ownership Build higher quality products Keep customers happy
  5. 5. WHAT IS TECHNICAL DEBT The concept of software complexity as debt was originally coined by Ward Cunningham in an experience report for OOPSLA ‘92 (*) Reference:
  6. 6. WHAT IS TECHNICAL DEBT? A big pile of deferred work can gum up a project, yet many of the items on the list don't appear on a project team's radar, especially if the focus is primarily on new product features. Yet removing accumulated sludge needs to be accounted for in planning! Therefore: Make the debt visible. Keep an explicit list Technical Debt
  7. 7. HOW DOES TECHNICAL DEBT HAPPEN? By not enforcing high quality standards Cutting corners to achieve a higher velocity to meet timelines As the velocity of system goes down, even more corners are cut
  8. 8. COST OF MAINTENANCE Product Burndown 100 90 80 Product Backlog 70 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 Iteration
  9. 9. COST OF MAINTENANCE Cost of Maintenance Maintenance Cost 0 1 2 3 4 5 6 7 8 9 Release
  10. 10. SIGNS OF TECHNICAL DEBT The code is considered part of a core or legacy system There is either no testing, or minimal testing surrounding the code ... the legacy system is not in a know state There is highly compartmentalized knowledge regarding the core/legacy system, and it may be supported by only one or two people in the company (over specialization)
  11. 11. SIGNS OF TECHNICAL DEBT It takes as long to fix defects caused be adding new functionality, as it does to add the new functionality Re-platforming ... and then repeat the mistakes of the past
  12. 12. AVOID TECHNICAL DEBT Development teams must curb over-optimism in assessing availability and capacity Management redirects attention from applying pressure to removing organizational impediments to progress Product Owners understand the iron triangle, ownership of risks, and impact of cutting quality ScrumMaster must prevent demonstration of any work that is not “done”
  13. 13. AVOID TECHNICAL DEBT Implement the Agile Technical practices: Continuous Integration Test Driven Development Refactoring Pair Programming
  14. 14. STRATEGIES FOR PAYING TECHNICAL DEBT Two strategies to consider: Highest interest rate first approach Lowest balance first approach
  15. 15. PAYING OFF TECHNICAL DEBT Described by Michael Feathers in “Working Effectively with Legacy code” Start by introducing Continuous Integration Write Automated Tests around customer reported defects Over a period of time a testing framework will be built up around the most brittle code
  16. 16. AND AVOID THIS ANTI- PATTERN There is a temptation to try and write a comprehensive testing framework around the entire product, but: This does not address the defects that the customer views as most important You may run out of money before you complete the framework, and You are not delivering new business value
  17. 17. IN CLOSING ... By focusing on reducing technical debt, we can: Better meet changing business needs reduce Total Cost of Ownership Build higher quality products Keep our customers happy
  18. 18. THANK YOU!
  19. 19. REFERENCES coalmine “Working Effectively with Legacy code,” by Michael Feathers “Test Driven Development: By Example”, by Kent Beck