One common question I hear from teams new to Agile is “How do you manage technical debt?”. Agile is often blamed for producing more technical debt than more traditional approaches – whether or not that’s true, everyone should have a mechanism for tackling it.
What is technical debt?
For anyone unfamiliar with the term, very basically, technical debt is any underlying element of your software that you should rework at some point in the future. Usually as a result of a previous decision or (in)activity that will impact the long-term value of your product, if left unaddressed.
It differs from a change initiated by the business in that it will usually be something either imperceptible to anyone non-technical and / or not involved in the technical implementation of the product (or certainly not obvious).
Ward Cunningham, credited with coining the term, describes this concept in the following way:
“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. Objects make the cost of this transaction tolerable. 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.”
He refers to object-oriented programming, but you’ll appreciate the concept applies universally, regardless of paradigm.
Unplanned technical debt
Unplanned technical debt is usually the consequence of external change, time pressures or a lack of understanding.
For example, maybe you produced a service that made heavy use of a rate-limited external API, on the assumption that your expected traffic volumes would never approach close to that value. Then, your product is a runaway success and you end up with more traffic than the rate limit allows, degrading performance.
Another example could be that your project made use of a UI library to produce your website, but now there are newer browser versions that the library does not handle, breaking layout and functionality in modern browsers.
You may have written an inefficient search algorithm, as you had to produce something very quickly at the time – but with further optimisation you could save significant server resources, needed for other processes going forwards.
From personal experience, I’ve had situations where I’ve discovered a much more elegant solution to a problem after the fact (where refactoring would improve pace of change and customer experience), towards the end of a project.
Planned technical debt
Sometimes you just have to accept that being able to produce something fast is occasionally better than (pro-actively) spending additional time on quality. For example, it’s quite valid to attempt to prove a concept in the quickest way possible, usually to answer an unknown factor (“will this work?”), over longer-term concerns.
This could result in things like a conscious decision not to include logging or perhaps you chose to skip adding any build automation, knowing that they would both be useful longer term. The key points with this approach is that the team has agreed the priorities, potential impact and any mitigation up front – the consequences of the situation are understood. As long as you address the issue later (or make a conscious decision to live with the issue), based on the business value balance, that’s fine.
When planned technical debt becomes particularly unhealthy, is when it emerges from a pressured, one-sided source – instead of as a natural result of collaborative effort. In Agile teams, this is usually the result of a dictatorial (bad) Product Owner – or someone else able to pressure the team into focusing on non-technical priorities, over the team’s overall agreed priorities. You could argue this is actually unplanned debt – but that divorces the responsibility from the stakeholders, who ultimately need to acknowledge that they have chosen this path.
The danger here is that the potential consequences of this type of technical debt are not understood. That’s a risky place to be – unbounded problems have a tendency to spread quickly – akin to spending on a credit card with no limit (and no one ever checking the balance). If your technical debt exceeds the value of the product, you’ve failed.
Successful software projects eventually need to achieve a level of balance between business functionality and technical architecture.
Too much focus on either side is not good. Businesses tend to focus on tactile features over practicality, while development teams want to produce academically elegant solutions that no one may actually want (or simply spend more time on it than the business value justifies).
Regardless on the cause of the debt, the way you tackle technical debt is largely the same. The team needs to prioritise effort together.
If your backlog refinement meetings are genuinely collaborative then you’d ideally have discussed and agreed your prioritisation of work to include a balance of business and technical needs – minimising debt in the first place.
While that may be the ideal, striking that balance isn’t always very successful, for a variety of reasons. Additionally, unplanned technical debt is a constant unseen threat – and it can build up at any time, even with the best of intentions.
Newly discovered technical debt should be bubbled-up (flagged) so that it can be addressed by the team. This means adding a story to the backlog with a description of the problem and optionally including a proposal to resolve it. When your backlog refinement meeting (grooming) occurs, you should have a mechanism to trigger triage of new stories, prompting a discussion about the issue. From there, your technical debt becomes like any other story being groomed:
- Flesh out the requirement – is it a problem?
- Break down any large chunks into smaller, manageable activities.
- Agree the acceptance criteria for it to be considered resolved (done).
- Prioritise based on the value to the product / feature.
- Add the stories to the appropriate sprint backlog.
- Review your balance of priorities again at the next planning session.
That’s it – when you become aware of technical debt, flag it by creating a story to represent it, let the team decide when and how it needs to be tackled – then deliver on your commitment.