The document discusses the concept of technical debt and how it differs from cruft. It explains that technical debt refers to strategic design decisions made to increase speed that require future work to pay back, while cruft is accidental messy or poorly-written code. The author warns that allowing cruft can lead teams into a trap where velocity is prioritized over quality, resulting in increasing cruft over time. The document provides suggestions for avoiding this trap, such as setting quality thresholds, making incremental fixes, and constantly cleaning code. It also recommends metrics for monitoring cruft and debt levels like code coverage, complexity, and coupling.

1. The Technical Debt Trap
Michael “Doc” Norton
@DocOnDev

2. Michael “Doc” Norton
Groupon
Director of
Technology
doc@groupon.com
@DocOnDev
Husband Father

3. GrandFather
He’s SOOO Cute!!

4. What is Technical Debt?

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

6. Ward
Cunningham
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

7. Ward
Cunningham
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

8. Ward
Cunningham
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

9. Technical Debt is a Good Idea

10. Technical Debt is a Good Idea
WTF?

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

12. Technical Debt is a Metaphor
Here Be Danger

13. Metaphors Rock
We Reason By Analogy
Can’t keep
running at thisBUILDING ON
pace A WEAK
FOUNDATION
IT’S RAINING MEN
(HALLELUJAH)
Puts pressure
on our design

14. Metaphorphosis
When Metaphors Go Wrong
Return on Investment
SHORT-TERM Fraudulent Credit Card
Inadvertent Reckless
AUTO LOAN
Debt in the Third PYRAMID SCHEME
HIGH INTEREST
Intentional Quadrant Long-Term
HOME LOAN
Loan Shark
VOLUNTARY
Prudent
Pragmatic Leverage Student Loan OPERATIONAL

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

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

17. Ummm... no.
[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.
http://www.youtube.com/watch?v=pqeJFYwnkjE&feature=player_embedded
YouTube.com ’09

18. Ummm... no.
[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.
http://www.youtube.com/watch?v=pqeJFYwnkjE&feature=player_embedded
YouTube.com ’09

19. [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.

20. ... confused it
with the idea that
you could write
code poorly ....

21. Clean Code
is Required
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.
http://www.youtube.com/watch?v=pqeJFYwnkjE&feature=player_embedded
YouTube.com ’09

22. Clean Code
is Required
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.
http://www.youtube.com/watch?v=pqeJFYwnkjE&feature=player_embedded
YouTube.com ’09

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

24. Is It Technical Debt?
Ask yourself ...
Is the code clean?
Is the code tested?
Is there a learning objective?
Is there a plan for payback?
Is the business truly informed?

25. Is It Technical Debt?
If you say no to even one...
Is the code clean?
Is the code tested?
Is there a learning objective?
Is there a plan for payback?
Is the business truly informed?
... then you don’t have Technical Debt

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

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

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

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

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

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

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

33. Technical Debt in other
fields
Construction
TE
R A
IB E
E L
D D
AN
S S
LE
CK
RE

34. Technical Debt in other
fields
Automotive
TE
R A
IB E
E L
D D
AN
S S
LE
CK
RE

35. Technical Debt in other
fields
Medical
NT
TE
E R
D V
IN A
N D
S A
ES
K L
EC
R

36. The Technical Debt Quadrant
LE CA L
SI B N I
“Let’s deploy and
N H T
E C EB
PO
gather more
ES T information.”
IRR D
N T
PE TE
M
INCO
http://martinfowler.com/bliki/TechnicalDebtQuadrant.html

37. DataSet aDs, qDs;
aDs = _dbConnector.UpdateAgentList();
qDs = _dbConnector.GetQueueList();
foreach (DataTable aTable in aDs.Tables) {
Cruft or Debt?
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
classclass EuropeanSwallow ...end classclass AfricanSwallow ... double
getSpeed() { return super.getSpeed - coconutLoad(); } double
coconutLoad() { return getLoadFactor() * _numberOfCoconuts; }end
classclass NorwegianSwallow ... double getSpeed() { return
(_isNailed) ? 0 : getBaseSpeed(_voltage); }end class

46. Cruft is a bad decision
Every Time
YOU ARE A PROFESSIONAL DEVELOPER
(Professionals behave ethically)
YOU ARE GOING TO CREATE UNINTENTIONAL CRUFT
(You can’t help it. It’s unintentional.)
YOU HAVE TO CLEAN UP THE EXISTING CRUFT
(Intent doesn’t alter Responsibility)

47. The Cost of “Technical Debt”
We did this
WORLD-WIDE TECHNICAL DEBT (INCLUDES HARDWARE)
$1 Trillion (by 2015)
PER BUSINESS APPLICATION
$1 Million

48. Grammy
Doesn’t
Love
Me!
Me!
Me!
It’s all about expectations

49. 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

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

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

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

53. 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

54. Monitoring Cruft/Debt
A few key metrics
Code Coverage
Cyclomatic Complexity
Coupling
Maintainability

55. Monitoring Cruft/Debt
Code Coverage
Code exercised by automated tests
Monitor test types separately
Don’t set a coverage target
100% coverage is a smell
Monitor trends, not points

56. Monitoring Cruft/Debt
Cyclomatic Complexity
Number of logical branches in code
Direct relationship with bugs
Typically high in concentrated areas
Reduce conditionals
Monitor trends, not points

57. Monitoring Cruft/Debt
Coupling
Interconnectedness of systems
Highly coupled is difficult to change
Afferent (Toward) and Efferent (Away)
Dependency Injection
Monitor trends, not points

58. Cruft/Debt Cards
Tie it to Business Value
Velocity
Scalability
Availability
Maintainability

59. Review
Technical Debt
Is a strategic design decision
Requires the business to be informed
Includes a pay-back plan
Cruft
HappensNeeds to be monitored and
cleanedIs NOT Technical Debt

60. Review
Technical Debt
Is a strategic design decision
Requires the business to be informed
Includes a pay-back plan
Cruft
HappensNeeds to be monitored and
cleanedIs (probably) NOT Technical Debt

61. Thank You!
The Technical Debt Trap
Michael “Doc” Norton
@DocOnDev