PEARL XIX : Effective Steps to reduce technical debt: An agile approach

PEARL XIX : Effective Steps to reduce technical debt: An agile approach

In every codebase, there are the dark corners and alleys developers fear. Code that’s impossibly brittle; code that bites back with regression bugs; code that when you attempt to follow, will drive you beyond chaos.

Ward Cunningham created a beautiful metaphor for the hard-to-change, error-prone parts of code when he likened it to financial debt. Technical debt prevents you from moving forward, from profiting, from staying “in the black.” As in the real world, there’s cheap debt, debt with an interest lower than you can make in a low-risk financial instrument. Then there’s the expensive stuff, the high-interest credit card fees that pile on even more debt.

The impact of accumulated technical debt can be decreased efficiency, increased cost, and extended delays in the maintenance of existing systems. This can directly jeopardize operations, undermining the stability and reliability of the business over time. It also can stymie the ability to innovate and grow

DB Systel, a subsidiary of Deutsche Bahn, is one of Germany’s leading information technology and communications providers, running approximately 500 high-availability business systems for its customers. In order to keep this complex environment—a mix of packaged and in-house–developed systems that range from mainframe to mobile—running efficiently while continuing to address the needs of its customers, DB Systel decided to embed processes and tools within its development and maintenance activities to actively address its technical debt.

DB Systel’s software developers have employed new tools during development so they can detect and correct errors more efficiently. Using a software analysis and measurement platform from CAST, DB Systel has been able to uncover architectural hot spots and transactions in its core systems that carry significant structural risk. DB Systel is now better able to track the nonfunctional quality characteristics of its systems and precisely measure changes in architecture- and code-level technical debt within these applications to prioritize the areas with highest impact.

By implementing this strategy at the architecture level, DB Systel has seen a reduction in time spent on error detection and an increased focus on leading-practice development techniques. The company also noticed a rise in employees’ intrinsic motivation as a result of using CAST. With an effective technical debt management process in place, DB Systel is mitigating the possibility of software deterioration while also enriching application quality.

Technical debt is a drag. It can kill productivity, making maintenance annoying, difficult, or, in some cases, impossible. Beyond the obvious economic downside, there’s a real psychological cost to technical debt. No developer enjoys sitting down to his computer in the morning knowing he’s about to face impossibly brittle, complicated source code. The frustration and helplessness thus engendered is often a root cause of more systemic problems, such as developer turnover— just one of the real economic costs of technical debt.

However, the consequences of failing to identify and measure technical debt can be significant. An application with a lot of technical debt may not be able to fulfill its business purpose and may never reach production. Or technical debt may require weeks or months of remedial refactoring before the application emerges into production. At best, it could reach production, but be limited in its ability to meet users’ needs.

Every codebase contains some measure of technical debt. One class of debt is fairly harmless: byzantine dependencies among bizarrely named types in stable, rarely modified recesses of  system. Another is sloppy code that is easily fixed on the spot, but often ignored in the rush to address higher-priority problems. There are many more examples.

This section outlines a general workflow and several tactics for dealing with the high-interest debt

In order to fix technical debt, team need to cultivate buy-in from stakeholders and teammates alike. To do this,they need to start thinking systemically. Systems thinking is long-range thinking. It is investment thinking. It’s the idea that effort you put in today will let you progress at a predictable and sustained pace in the future.

Technical debt (also known as design debt or code debt) is a neologism metaphor referring to the eventual consequences of poor software architecture and software development within a code-base. The debt can be thought of as work that needs to be done before a particular job can be considered complete. If the debt is not repaid, then it will keep on accumulating interest, making it hard to implement changes later on. Unaddressed technical debt increases software entropy.

As a change is started on a codebase, there is often the need to make other coordinated changes at the same time in other parts of the codebase or documentation. The other required, but uncompleted changes, are considered debt that must be paid at some point in the future. Just like financial debt, these uncompleted changes incur interest on top of interest, making it cumbersome to build a project. Although the term is used in software development primarily, it can also be applied to other professions.

Common causes of technical debt include (a combination of):

  • Business pressures, where the business considers getting something released sooner before all of the necessary changes are complete, builds up technical debt comprising those uncompleted changes
  • Lack of process or understanding, where businesses are blind to the concept of technical debt, and make decisions without considering the implications
  • Lack of building loosely coupled components, where functions are hard-coded, when business needs change, the software is inflexible.
  • Lack of test suite, which encourages quick and risky band-aids to fix bugs.
  • Lack of documentation, where code is created without necessary supporting documentation. That work to create the supporting documentation represents a debt that must be paid.
  • Lack of collaboration, where knowledge isn’t shared around the organization and business efficiency suffers, or junior developers are not properly mentored
  • Parallel development at the same time on two or more branches can cause the build up of technical debt because of the work that will eventually be required to merge the changes into a single source base. The more changes that are done in isolation, the more debt that is piled up.
  • Delayed refactoring – As the requirements for a project evolve, it may become clear that parts of the code have become unwieldy and must be refactored in order to support future requirements. The longer that refactoring is delayed, and the more code is written to use the current form, the more debt that piles up that must be paid at the time the refactoring is finally done.
  • Lack of knowledge, when the developer simply doesn’t know how to write elegant code.

“Interest payments” are both in the necessary local maintenance and the absence of maintenance by other users of the project. Ongoing development in the upstream project can increase the cost of “paying off the debt” in the future. One pays off the debt by simply completing the uncompleted work.

The build up of technical debt is a major cause for projects to miss deadlines. It is difficult to estimate exactly how much work is necessary to pay off the debt. For each change that is initiated, an uncertain amount of uncompleted work is committed to the project. The deadline is missed when the project realizes that there is more uncompleted work (debt) than there is time to complete it in. To have predictable release schedules, a development team should limit the amount of work in progress in order to keep the amount of uncompleted work (or debt) small at all times.

“As an evolving program is continually changed, its complexity, reflecting deteriorating structure, increases unless work is done to maintain or reduce it.”
— Meir Manny Lehman, 1980
While Manny Lehman’s Law already indicated that evolving programs continually add to their complexity and deteriorating structure unless work is done to maintain it, Ward Cunningham first drew the comparison between technical complexity and debt in a 1992 experience report:

“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… The danger occurs when the debt is not repaid. Every minute spent on not-quite-right code counts as interest on that debt. Entire engineering organizations can be brought to a stand-still under the debt load of an unconsolidated implementation, object-oriented or otherwise.”
— Ward Cunningham, 1992
In his 2004 text, Refactoring to Patterns, Joshua Kerievsky presents a comparable argument concerning the costs associated with architectural negligence, which he describes as “design debt”.

“…doing things the quick and dirty way sets us up with a technical debt, which is similar to a financial debt. Like a financial debt, the technical  debt incurs interest payments, which come in  the form of the extra effort that we have to do in  future development because of the quick and dirty  design choice. We can choose to continue paying  the interest, or we can pay down the principal by  refactoring the quick and dirty design into the  better design. Although it costs to pay down the
principal, we gain by reduced interest payments  in the future.”

–Martin Fowler

Technical Debt” refers to delayed technical  work that is incurred when technical short  cuts are taken, usually in pursuit of calendar driven software schedules. Just like financial  debt, some technical debts can serve valuable  business purposes. Other technical debts are  simply counterproductive. The ability to take on
debt safely, track their debt, manage their debt, and pay down their debt varies among different  organizations. Explicit decision making before  taking on debt and more explicit tracking of debt  are advised.

–Steve McConnell

Activities that might be postponed include documentation, writing tests, attending to TODO comments and tackling compiler and static code analysis warnings. Other instances of technical debt include knowledge that isn’t shared around the organization and code that is too confusing to be modified easily.

In open source software, postponing sending local changes to the upstream project is a technical debt

 The basic workflow for tackling technical debt—indeed any kind of improvement—is repeatable. Essentially, there are four:

  1. Identify where are the debt. How much is each debt item affecting  company’s bottom line and team’s productivity?
  2. Build a business case and forge a consensus on priority with those affected by the debt, both team and stakeholders.
  3. Fix the debt  on the  chosen item, head on with proven tactics.
  4. Repeat. Go back to step 1 to identify additional debt and hold the line on the improvements  made.

Agile Approach to Technical Debt

Involve the Product Owner and “promote” him to be the sponsor of technical debt reduction.

Sometimes it’s hard to find debt, especially if a team is new to a codebase. In cases where there’s no collective memory or oral tradition to draw on, team can use a static analysis tool such as NDepend ( to probe the code for the more troublesome spots.

Determining test coverage  can be another valuable tool for discovering hidden debt.

Use the log feature of  version control system to generate a report of changes over the last month or two. Find the parts of the system that receive the most activity, changes or additions, and scrutinize them for technical debt. This will help to find the bottlenecks that are challenging  today; there’s very little value in fixing debt in those parts of your system that change rarely.

Inventory and structure known technical debt

Having convinced the product owner it is time to collect and inventory known technical problems and map them on a structure that visualizes the system and project landscape.

It is not about completely understanding all topics. It is about finding a proper structure, identifying the most important issues and mapping those onto the structure. It’s about extracting knowledge about the systems from the heads to develop a common picture of existing technical problems.

Therefore write the names / identifiers of all applications and modules individual own on cards. These cards shall be pinned on a whiteboard. In the next step extract to-do’s (to solve existing problems) from all documentation media used (wiki, jira, confluence, code documentation, paper), write them on post-its and stuck them next to the application name it belongs to.This board shall be accessible to all team members over a period of some days. Every team member was responsible to complete, restructure, and correct the board during this period so that they could go on with a round portfolio of the existing debt in the systems.

Having collected and understood the work to reduce the technical debt within the systems the team now need a baseline for defining a good strategy – a repayment plan. Therefore  Costs and benefits shall be estimated. 

Obtaining consensus is key. We want the majority of team members to support the current improvement initiative e selected.Luke Hohmann’s “Buy a Feature” approach from his book Innovation Games ( will help to get consensus.

  1. Generate a short list (5-9 items) of things you want to improve. Ideally these items are in your short-term path.
  2. Qualify the items in terms of difficulty. we can use the abstract notion of a T-shirt size: small, medium, large or extra-large
  3. Give your features a price based on their size. For example, small items may cost $50, medium items $100, and so on.
  4. Give everyone a certain amount of money. The key here is to introduce scarcity into the game. You want people to have to pool their money to buy the features they’re interested in. You want to price, say, medium features at a cost where no one individual can buy them. It’s valuable to find where more than a single individual sees the priority since you’re trying to build consensus.
  5. Run a short game, perhaps 20 or 30 minutes in length, where people can discuss, collude, and pitch their case. This can be quite chaotic and also quite fun, and you’ll see where the seats of influence are in your team.
  6. Review the items that were bought and by what margins they were bought. You can choose to rank your list by the purchased features or, better yet, use the results of the Buy a Feature game in combination with other techniques, such as an awareness of the next release plan.

Taking on some judicious technical debt can be an appropriate decision to meet schedules or to prototype a new feature set, as long as the decision was made with a clear understanding of the costs involved later in the project, such as code refactoring.

As Martin Fowler says, “The useful distinction  isn’t between debt or non-debt, but between prudent and reckless  debt.”


Technical debt actually begets more tech debt over time, and its state diagram is depicted.

Load Testing as a Practice to identify Technical Debt

Load testing exposes weaknesses in an application that cannot be found through traditional functional testing. Those weaknesses are generally reflected in the application’s inability to scale appropriately. Testers are also typically  already planning to perform load testing at some point prior to  the production release of the application.

Load testing involves enabling virtual users to execute predetermined actions simultaneously against the application. The  scripts exercise features either singly or in sequences expected  to be common among production users.

Load testing looks at the characteristics of an application under a simulated load, similar to the way it might operate in a production environment. At the highest level, it determines if an application will support the number of simultaneous users specified in the project requirements.

However, it does more than that. By looking at system characteristics as you increase the number of simultaneous users, you  can make some useful statements regarding what resources  are being stressed, and where in the application they are being stressed. With this information, the team can identify weaknesses in the application that are generally the result of incurring  technical debt, therefore providing the basis for identifying the  debt.

Some automation and measurement tools are required to successfully identify and assess technical debt with load testing.

Coding / Testing Practices

Management has to make the time  through proactive investment, but so does the team. Each team member needs to invest in their own knowledge and  education on how to write clean code, their business domain  and how to do their jobs optimally. While teams learn during  the project through retrospectives, design reviews and pair  programming, teams should learn agile engineering practices  for design, development and testing. Whether through courses,  conferences, user groups, podcasts, web sites or books – there  are many options for learning better coding practices to reduce technical debt

Design Principles and Techniques

Additionally, architects need to learn about evolutionary design principles and refactoring techniques for fixing poor designs today and building better designs tomorrow. Lastly, a governance group should meet periodically to review performance and plan future system
changes to further reduce technical debt.

Definition of Done

Establish a common “definition of done” for each requirement, user story or use case and ensure its validated with the business before development begins. A simple format  such as “this story is done when: <list of criteria>” works well. The Product Owner presents “done” to the Developers, User
Interface Designers, Testers and Analysts and together they collaboratively work out the finer implementation details. Set expectations with developers that only stories meeting “done” (as validated by the testers) will be accepted and contribute towards velocity. Similarly, set expectations with management and analysts that only stories that are “ready” are scheduled for development to ensure poor requirements don’t cause further technical debt.

In all popular languages and platforms today, open source and commercial tools are available to automate builds, the continuous integration of code changes, unit testing, acceptance testing, deployments, database setup, performance testing and many other common manual activities. In addition to reducing manual effort, automation reduces the risk of mistakes and over-reliance on one individual for performing critical activities. First setup automated builds ( Ant, nAnt or rake), followed by continuous integration ( Hudson). Next setup automated unit testing (JUnit, NUnit or RSpec) and acceptance testing ( FitNesse and Selenium). Finally setup automated deployments (r Capistrano or custom
shells scripts,). It’s amazing what a few focused team members can accomplish in a relatively short period of time if given time to focus on automating common activities to reduce technical debt.

Consider rating and rewarding developers on the quality of their code. In some cases, fewer skilled developers may be better than volumes of mediocre resources whose work may require downstream reversal of debt. Regularly run code complexity reviews and technical debt assessments, sharing the results across the team. Not only can specific examples help the team improve, but trends can signal that a project is headed in the wrong direction or encountering unexpected complexity.


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