Technical Debt

Software systems are prone to the build up of cruft – deficiencies in internal quality that make it harder than it would ideally be to modify and extend the system further. Technical Debt is a metaphor, coined by Ward Cunningham, that frames how to think about dealing with this cruft, thinking of it like a financial debt. The extra effort that it takes to add new features is the interest paid on the debt.

Martins Fowlers description of Technical Debt

The metaphor of debt is sometimes used to justify neglecting internal quality. The argument is that it takes time and effort to stop cruft from building up. If there new features that are needed urgently, then perhaps it’s best to take on the debt, accepting that this debt will have to be managed in the future.

The danger here is that most of the time this analysis isn’t done well. Cruft has a quick impact, slowing down the very new features that are needed quickly. Teams who do this end up maxing out all their credit cards, but still delivering later than they would have done had they put the effort into higher internal quality. Here the metaphor often leads people astray, as the dynamics don’t really match those for financial loans. Taking on debt to speed delivery only works if you stay below the design payoff line of the Design Stamina Hypothesis, and teams hit that line in weeks rather than months.

There are regular debates whether different kinds of cruft should be considered as debt or not. I found it useful to think about whether the debt is acquired deliberately and whether it is prudent or reckless – leading me to the Technical Debt Quadrant.

Technical Debt Quadrant


See also The Human Cost of Technical Debt – the human side of the problem.  And, make no mistake — in business, all human problems are also business problems,viewed with a wide enough lens.  Unhappy humans are unhappy workers, and unhappy workers are less productive.  Yet, this angle of technical debt is seldom discussed, in my experience.

  • Unpleasant Work
  • Team Infighting
  • Atrophied Skills
  • The Hidden Business Cost: Turnover and Attrition

Agile Manifesto

We are uncovering better ways of developing
software by doing it and helping others do it.
Through this work we have come to value:

Individuals and interactions over processes and tools
Working software over comprehensive documentation
Customer collaboration over contract negotiation
Responding to change over following a plan

That is, while there is value in the items on
the right, we value the items on the left more.

And the principles behind the agile manifesto are:

Our highest priority is to satisfy the customer
through early and continuous delivery
of valuable software.

Welcome changing requirements, even late in
development. Agile processes harness change for
the customer’s competitive advantage.

Deliver working software frequently, from a
couple of weeks to a couple of months, with a
preference to the shorter timescale.

Business people and developers must work
together daily throughout the project.

Build projects around motivated individuals.
Give them the environment and support they need,
and trust them to get the job done.

The most efficient and effective method of
conveying information to and within a development
team is face-to-face conversation.

Working software is the primary measure of progress.

Agile processes promote sustainable development.
The sponsors, developers, and users should be able
to maintain a constant pace indefinitely.

Continuous attention to technical excellence
and good design enhances agility.

Simplicity–the art of maximizing the amount
of work not done–is essential.

The best architectures, requirements, and designs
emerge from self-organizing teams.

At regular intervals, the team reflects on how
to become more effective, then tunes and adjusts
its behavior accordingly.