Technical Debt has become a catch-all phrase for any code that needs to be re-worked. Much like Refactoring has become a catch-all phrase for any activity that involves changing code. These fundamental misunderstandings and comfortable yet mis-applied metaphors have resulted in a plethora of poor decisions. What is technical debt? What is not technical debt? Why should we care? What is the cost of misunderstanding? What do we do about it? Doc discusses the origins of the metaphor, what it means today, and how we properly identify and manage technical debt.

1. The
Technical Debt Trap
Doc Norton
doc@groupon.com
@DocOnDev

2. Doc Norton!
Global Director of Engineering Culture!
doc@groupon.com | @DocOnDev
Husband Father

3. Grandfather!

4. What is Technical Debt?

5. Shipping first time code is like going into debt.
OOPSLA ‘92
Ward Cunningham

6. Shipping first time code is like going into debt.
A little debt speeds development so long as it
is paid back promptly with a rewrite.
OOPSLA ‘92
Ward Cunningham

7. The danger occurs when the debt is not repaid.
Every minute spent on not-quite-right code
counts as interest on that debt.
OOPSLA ‘92
Ward Cunningham

8. The danger occurs when the debt is not repaid.
Every minute spent on not-quite-right code
counts as interest on that debt.
OOPSLA ‘92
Ward Cunningham

9. Technical Debt is Good

10. WTF?
Technical Debt is Good

11. Technical Debt is Good
Strategic Design Decision
❖ Allow for Rapid Delivery!
❖ To Elicit Quick Feedback!
❖ And Correct Design

12. Technical Debt is Good
Indication of Learning
❖ Now know what you need!
❖ Implementation doesn’t match!

13. Technical Debt is a Metaphor
Here Be Danger

14. Metaphor’s Rock
We Reason by Analogy
Building on
a weak
foundation
Puts pressure on
our design
Can’t keep running
at this pace
It’s raining men
(hallelujah)

15. Metaphorphosis
When Metaphors Go Wrong
SHORT-TERM
Long-Term
INADVERTENT RECKLESS
DEBT IN THE THIRD
QUADRANTPrudent
Intentional
Credit Card
FRAUDULENT
AUTO LOAN
Student Loan
HOME LOAN
Loan Shark
Return on Investment
PYRAMID SCHEME
VOLUNTARY
PRAGMATIC LEVERAGE
HIGH INTEREST
OPERATIONAL

16. Metaphorphosis
When Metaphors Go Wrong
“QUICK AND DIRTY”
MARTIN FOWLER
HTTP://WWW.MARTINFOWLER.COM/BLIKI/TECHNICALDEBT.HTML
“SLOPPY”
DAVID LARIBEE
HTTP://MSDN.MICROSOFT.COM/EN-US/MAGAZINE/EE819135.ASPX
“JUST HACK IT IN”
STEVE MCCONNELL
HTTP://BLOGS.CONSTRUX.COM/BLOGS/STEVEMCC/ARCHIVE/2007/11/01/TECHNICAL-DEBT-2.ASPX
“CUT A LOT OF CORNERS”
JAMES SHORE
HTTP://JAMESSHORE.COM/BLOG/CARDMEETING/VOLUNTARY-TECHNICAL-DEBT.HTML

17. The Technical Debt Quadrant
http://martinfowler.com/bliki/TechnicalDebtQuadrant.html

18. [Many] have explained the debt metaphor and
confused it with the idea that you could write code
poorly with the intention of doing a good job later.
YouTube ‘09
Ummm… No.
http://www.youtube.com/watch?v=pqeJFYwnkjE&feature=player_embedded

19. confused the debt
metaphor with the
idea that you could
write code poorly

20. The ability to pay back debt [...] depends upon
you writing code that is clean enough to be able to
refactor as you come to understand your problem.
YouTube ‘09
Clean Code is
Required
http://www.youtube.com/watch?v=pqeJFYwnkjE&feature=player_embedded

21. The ability to pay back debt [...] depends upon
you writing code that is clean enough to be able to
refactor as you come to understand your problem.
YouTube ‘09
Clean Code is
Required
http://www.youtube.com/watch?v=pqeJFYwnkjE&feature=player_embedded

22. Twitter ‘09
Dirty Code is a Bad
Idea
Dirty code is to technical debt as the pawn
broker is to financial debt.!
http://twitter.com/WardCunningham/status/3742903303
Don’t think you are ever going to get your
code back.

23. Is it Technical Debt?
Ask yourself…
❖ Is the code clean?!
❖ Is the code tested?!
❖ Is there a learning objective or event?!
❖ Is there a plan for payback?!
❖ Is the business truly informed?

24. Is it Technical Debt?
If you say no to even one…
❖ Is the code clean?!
❖ Is the code tested?!
❖ Is there a learning objective or event?!
❖ Is there a plan for payback?!
❖ Is the business truly informed?
... then you don’t have Technical Debt

25. You have a mess
Mess (noun)
❖ Disorderly accumulation, heap, or jumble!
❖ A state of embarrassing confusion!
❖ An unpleasant or difficult situation

26. You have cruft
Cruft (noun)
❖ An unpleasant substance!
❖ The result of shoddy construction!
❖ Redundant, old or improperly written code

27. Chill. It’s just semantics, man.
Just Semantics?
Technical Debt is Good

28. Chill. It’s just semantics, man.
Just Semantics?
Technical Debt is GoodQuick and Dirty is Technical DebtQuick and Dirty is Good

29. Chill. It’s just semantics, man.
Just Semantics?
Quick and Dirty is GoodQuick and Dirty is Good

30. The Technical Debt Quadrant
http://martinfowler.com/bliki/TechnicalDebtQuadrant.html

31. The Technical Debt Quadrant
http://martinfowler.com/bliki/TechnicalDebtQuadrant.html
“Let’s deploy and
gather more
information.”

32. Technical Debt in Other Fields

33. Technical Debt in Other Fields

34. Technical Debt in Other Fields

35. Technical Debt in Other Fields
RECKLESS AND DELIBERATE
RECKLESS AND DELIBERATE
RECKLESS AND INADVERTENT

36. The Technical Debt Quadrant
http://martinfowler.com/bliki/TechnicalDebtQuadrant.html
IRRESPONSIBLE
INCOMPETENT
“Let’s deploy and
gather more
information.”
TECHNICAL
DEBT

37. Cruft or Debt?
DataSet aDs, qDs;!
aDs = _dbConnector.UpdateAgentList();!
qDs = _dbConnector.GetQueueList();!
foreach (DataTable aTable in aDs.Tables) {!
foreach (DataRow aRow in aTable.Rows) {!
foreach (DataColumn aColumn in aTable.Columns) {!
DataSet asDs = _dbConnector.GetAgentSkills(aRow[aColumn].ToString());//AgentId!
foreach (DataTable asTable in asDs.Tables) {!
foreach (DataRow asRow in asTable.Rows) {!
foreach (DataColumn asColumn in asTable.Columns) {!
foreach (DataTable qTable in qDs.Tables) {!
foreach (DataRow qRow in qTable.Rows) {!
foreach (DataColumn qColumn in qTable.Columns) {!
DataSet sqDs = _dbConnector.GetSkillsForQueue(qRow[qColumn].ToString());!
foreach (DataTable sqTable in sqDs.Tables) {!
foreach (DataRow sqRow in sqTable.Rows) {!
foreach (DataColumn sqColumn in sqTable.Columns) {!
foreach (string skill in sqRow[sqColumn].ToString().Split(paramDelimStr)) {!
if (skill == asRow[asColumn].ToString()) {!
try {!
_dbConnector.SetAgentQueueSkill(aRow[aColumn].ToString(),!
qRow[qColumn].ToString(),!
skill);!
}!
catch { continue; }!
}!
}!
}!
}!
}!
}!
}!
}!
}!
}!
}!
}!
}!
}
http://thedailywtf.com/Series/2010/3/CodeSOD.aspx

38. Cruft or Debt?
DataSet aDs, qDs;!
aDs = _dbConnector.UpdateAgentList();!
qDs = _dbConnector.GetQueueList();!
foreach (DataTable aTable in aDs.Tables) {!
foreach (DataRow aRow in aTable.Rows) {!
foreach (DataColumn aColumn in aTable.Columns) {!
DataSet asDs = _dbConnector.GetAgentSkills(aRow[aColumn].ToString());//AgentId!
foreach (DataTable asTable in asDs.Tables) {!
foreach (DataRow asRow in asTable.Rows) {!
foreach (DataColumn asColumn in asTable.Columns) {!
foreach (DataTable qTable in qDs.Tables) {!
foreach (DataRow qRow in qTable.Rows) {!
foreach (DataColumn qColumn in qTable.Columns) {!
DataSet sqDs = _dbConnector.GetSkillsForQueue(qRow[qColumn].ToString());!
foreach (DataTable sqTable in sqDs.Tables) {!
foreach (DataRow sqRow in sqTable.Rows) {!
foreach (DataColumn sqColumn in sqTable.Columns) {!
foreach (string skill in sqRow[sqColumn].ToString().Split(paramDelimStr)) {!
if (skill == asRow[asColumn].ToString()) {!
try {!
_dbConnector.SetAgentQueueSkill(aRow[aColumn].ToString(),!
qRow[qColumn].ToString(),!
skill);!
}!
catch { continue; }!
}!
} } } } } } } } } } } } }
http://thedailywtf.com/Series/2010/3/CodeSOD.aspx

39. Cruft or Debt?
DataSet aDs, qDs, asDs, sqDs;!
aDs = _dbConnector.UpdateAgentList();!
qDs = _dbConnector.GetQueueList();!
!
foreach (DataRow aRow in aDS.Tables[0].Rows) {!
String agentID = aRow[“AgentId”].ToString();!
asDs = _dbConnector.GetAgentSkills(agentID);!
foreach (DataRow asRow in asDs.Tables[0].Rows) {!
String agentSkill = asRow[“Skill”].ToString();!
foreach (DataRow qRow in qDs.Tables[0].Rows) {!
queueName = qRow[“QueueName”].ToString();!
sqDs = _dbConnector.GetSkillsForQueue(queueName);!
foreach (DataRow sqRow in sqDs.Tables[0].Rows) {!
foreach (string skill in sqRow[“Skills”].ToString().Split(paramDelimStr)) {!
if (skill == agentSkill) {!
try { _dbConnector.SetAgentQueueSkill(agentID, queueName, skill); }!
catch { continue; }!
}!
}!
}!
}!
}!
}
http://thedailywtf.com/Series/2010/3/CodeSOD.aspx

40. Cruft or Debt?
AgentList agents = new AgentList(_dbConnector.UpdateAgentList());!
QueueList queues = new QueueList(_dbConnector.GetQueueList());!
!
foreach (Agent agent in agents) {!
foreach (Skill agentSkill in agent.skills) {!
foreach (Queue queue in queues) {!
foreach (Skill queueSkill in queue.skills.Where(x => x == agentSkill)) {!
try {_dbConnector.SetAgentQueueSkill(agent.agentID, queue.name, agentSkill); }!
catch { continue; }!
}!
}!
}!
}
http://thedailywtf.com/Series/2010/3/CodeSOD.aspx

41. Cruft or Debt?
if ((customer.state == “AL” && customer.type ==!
CustomerType.GENERAL_AGENT && customer.revenue > 100000)!
|| (customer.type == CustomerType.RETRO_AGENT &&!
(customer.state == “WI” || customer.state == “IL”))!
|| (customer.type == CustomerType.FED_MANAGEMENT &&!
customer.revenue > 150000)) { ... }

42. Cruft or Debt?
// If customer is Federally Regulated!
if ((customer.state == “AL” && customer.type ==!
CustomerType.GENERAL_AGENT && customer.revenue > 100000)!
|| (customer.type == CustomerType.RETRO_AGENT &&!
(customer.state == “WI” || customer.state == “IL”))!
|| (customer.type == CustomerType.FED_MANAGEMENT &&!
customer.revenue > 150000)) { ... }

43. Cruft or Debt?
if (customer.isFederallyRegulated()) { ... }

44. Cruft or Debt?
double getSpeed() {!
switch (_type) {!
case EUROPEAN:!
return getBaseSpeed();!
case AFRICAN:!
return getBaseSpeed() - getLoadFactor() * _numberOfCoconuts;!
case NORWEGIAN_BLUE:!
return (_isNailed) ? 0 : getBaseSpeed(_voltage);!
}!
throw new RuntimeException ("Should be unreachable");!
}!
http://www.refactoring.com/catalog/replaceConditionalWithPolymorphism.html

45. Cruft or Debt?
class Swallow ...!
double getSpeed() { return getBaseSpeed(); }!
end class!
!
class EuropeanSwallow ...!
end class!
!
class AfricanSwallow ...!
double getSpeed() { return super.getSpeed - coconutLoad(); }!
double coconutLoad() { return getLoadFactor() * _numberOfCoconuts; }!
end class!
!
class NorwegianSwallow ...!
double getSpeed() { return (_isNailed) ? 0 : getBaseSpeed(_voltage); }!
end class

46. Cruft is a bad decision
Every Time
❖ You are a professional developer!
❖ You’re going to create unintentional cruft!
❖ You have to clean up the existing cruft

47. The Trap
Cruft begets Cruft
❖ Precedent for speed over quality!
❖ Expectation of increased velocity!
❖ Cruft slows you down!
❖ Must write more cruft to keep up!
❖ Ask permission to do your job correctly

48. Avoid The Trap
Thresholds set false expectations
http://blog.castsoftware.com/wp-content/uploads/2011/04/Technical-Debt-Software-Quality1.jpg

49. Avoid The Trap
Incremental fixes fail
http://www.jacoozi.com/blog/wp-content/uploads/2007/01/refactoring_coc_big.jpg

50. http://www.jacoozi.com/blog/wp-content/uploads/2007/01/refactoring_coc_big.jpg

51. Avoid The Trap
Clean Constantly
❖ Never make an intentional mess!
❖ Monitor your “Technical Debt”!
❖ Follow the Boy Scout Rule!
❖ Remember quality is your responsibility!
❖ NEVER ask permission to do your job correctly

52. Monitoring Cruft/Debt
A few key metrics
❖ Code Coverage!
❖ Code Complexity!
❖ Coupling!
❖ Maintainability

53. Monitoring Cruft/Debt
Code Coverage
❖ Code exercised by automated tests!
❖ Monitor types of tests separately!
❖ Don’t set a coverage target!
❖ 100% coverage is a smell!
❖ Monitor Trends, Not Points

54. Monitoring Cruft/Debt
Complexity
❖ Count of logical branches in code!
❖ Direct relationship with bugs!
❖ Typically high in concentrated areas!
❖ Reduce conditionals!
❖ Monitor Trends, Not Points

55. Monitoring Cruft/Debt
Coupling
❖ Interconnectedness of systems!
❖ Highly coupled is difficult to change!
❖ Afferent (toward) and Efferent (away)!
❖ Dependency Injection!
❖ Monitor Trends, Not Points

56. Monitoring Cruft/Debt
Make stories for cruft
❖ Velocity!
❖ Scalability!
❖ Availability!
❖ Maintainability

57. Review
Technical Debt
❖ A strategic design decision!
❖ Requires business to be informed!
❖ Includes a pay-back plan
Cruft
❖ Happens!
❖ Needs to be monitored and cleaned!
❖ Is NOT Technical Debt

58. Review
Technical Debt
❖ A strategic design decision!
❖ Requires business to be informed!
❖ Includes a pay-back plan
Cruft
❖ Happens!
❖ Needs to be monitored and cleaned!
❖ Is NOT Technical Debt
NEVER
ask
perm
ission
to do your job
correctly

59. The
Technical Debt Trap
Doc Norton!
doc@groupon.com!
@DocOnDev
Comments / Questions?

60. The
Technical Debt Trap
Doc Norton!
doc@groupon.com!
@DocOnDev
Thank You!