What is Legacy Code?
"Legacy code" is a term used far and wide in the IT industry. However, the most relevant definition is outdated software still in use but represents business risk because it is difficult to operate or change.
The term outdated signifies that it was developed using now-deprecated languages, old frameworks, or technologies that no longer align with current standards.
There are several reasons why it may be hard to change:
- The old technologies tend to use different paradigms that are harder to grasp for developers who are not skilled in them.
- Documentation may be missing, even when it comes to primary sources from the technology vendors.
- The people who created it might not be available to the company anymore.
The risk may not materialise: a legacy system can perform fine as long as the needs of the business remain minimal or unchanged. But it is still to some extent a ticking time bomb.
Key characteristics of legacy code:
- Old but functional: It was created long ago and might still perform its original task.
- Hard to understand: It can be difficult to understand or modify because it was written in old languages by people who might no longer be around, and the documentation might be missing or inadequate.
- Risky to change: Changing legacy code can be risky because it might break critical functions that the business relies on. This is often because the code is poorly understood or wasn't written with modern best practices in mind.
In the video above, Anders Clark, one of our consultants, discusses the issues legacy code can present, from technical debt to security vulnerabilities and the inability to integrate with modern technologies.
What is Technical Debt?
Technical debt is a concept in software development that refers to the extra work that arises when an easy-to-implement approach is chosen, even though we are aware that more work will be needed in the future to undo the negative aspects of this approach. This is done because it allows us to achieve business value quickly, which can have many benefits, such as gaining more insights into both business and technical domains, which can even help us pay down the debt in the future. So it is not an inherently bad thing if it is managed well.
Key considerations regarding technical debt:
- Shortcuts today, costs tomorrow: You create technical debt when taking a shortcut in your code today that you know will cost more work in the future. Make sure you know what values you gain by taking the shortcut, and stay realistic about the costs you are incurring.
- It slows down development: As technical debt builds up, it can make future changes harder and more time-consuming. Quick fixes pile up, making the codebase more complex and harder to work with.
- It needs repayment: Like financial debt, technical debt must be paid back by cleaning up the quick-and-dirty code, which takes time and resources.
The difference between legacy code and technical debt
Legacy code and technical debt are often discussed together. But what exactly is the difference between them?
Legacy code refers to outdated, hard-to-modify code. Technical debt is the extra work required in the future because shortcuts were taken during initial coding, leading to increased complexity and maintenance challenges.
Why is legacy code a problem?
Some aspects of legacy code are not in our control, but managing the legacy code risk has to be an essential part of strategic considerations for your development roadmap. If addressing legacy code is not woven into your ways of working or prioritised by the business, you risk several consequences, such as poor maintainability, lesser security, integration challenges with more modern technologies, and reduced productivity.
Let’s dive deeper into each problem area to understand the wider implications.
Maintenance Challenges
- Complexity: Legacy systems are often built over many years with multiple layers of modifications, making them complex and hard to understand.
- Documentation gaps: In many cases, the original developers are no longer available, and documentation is either insufficient or non-existent, leading to a steep learning curve for new developers.
- Competence loss: Code in languages like Pascal and Cobol may lose its remaining maintainers as the current generation of Pascal and Cobol developers retire.
Security Risks
Older codebases are more likely to contain vulnerabilities that modern security practices and tools are designed to mitigate. This poses a significant risk to data integrity and confidentiality.
Challenges Retaining and Attracting Talent
Working with legacy code can be quite painful and affect your developers' day-to-day job satisfaction. Companies that rely heavily on legacy code are frequently perceived as outdated and resistant to change, and many of the best developers want to work with modern tech stacks and ways of working.
Integration Issues
Legacy systems can struggle to integrate with new technologies, limiting the ability to leverage advancements in areas such as cloud computing, artificial intelligence, and modern development frameworks.
Operational Inefficiency
As technology evolves, the cost and effort required to maintain legacy systems increase, leading to inefficiencies and higher operational costs.
As mentioned in the video, Anders explains the critical signs that indicate it’s time to address your legacy code. These include increased bug reports, slowing performance, and the inability to support new business requirements.
How to Approach and Fix Legacy Code
While it may seem daunting to begin addressing your legacy code, a holistic approach and a clear plan can help you make impactful changes quickly. Below is a list of recommendations for fixing legacy code sustainably.
Assessment and Planning
- Audit the current system: Conduct a thorough audit of the existing legacy code to understand its structure, dependencies, and areas of risk.
- Set clear objectives: Define what you aim to achieve by updating the legacy code, improving performance, enhancing security, or enabling new features.
Incremental Refactoring
- Prioritise by impact: Start by refactoring the parts of the codebase that have the most significant impact on performance and security.
- Continuous integration: Use continuous integration practices to ensure that refactoring efforts do not introduce new issues into the system.
Use Modern Tools and Practices:
- Automated testing: Implement automated testing to catch issues early and ensure that changes do not break existing functionality.
- Version control: Utilise modern version control systems to manage changes and collaborate effectively.
Training and Documentation:
- Upskill your team: Invest in training your development team on modern technologies and best practices for maintaining and refactoring legacy code.
- Improve documentation: As you refactor, create comprehensive documentation to support future maintenance efforts.
Get Expert Help
- Partner with us: Ensure a smooth and successful legacy code evolution by partnering with our team. Click here to book a free meeting and start solving your legacy code challenges today.
In the final video, Anders outlines a strategic approach to tackling legacy code projects, emphasising the importance of planning, modern tools, and continuous improvement.
Conclusion
Legacy code poses significant challenges but also presents opportunities for improvement and innovation. By understanding the issues, recognising when to act, and adopting a structured approach to modernisation, businesses can mitigate risks and unlock new potential.
Engaging with experts like Anders Clark and leveraging their insights can guide your organisation through the complexities of legacy code transformation.
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Article links
If you would like to dive deeper into the topics of legacy code and technical debt, here are some of our favourite resources:
- McKinsey on technical debt: https://www.mckinsey.com/capabilities/mckinsey-digital/our-insights/demystifying-digital-dark-matter-a-new-standard-to-tame-technical-debt
- Blog post with key points of Legacy System - Working Effectively with Legacy Code: https://understandlegacycode.com/blog/key-points-of-working-effectively-with-legacy-code/
Books :
- Legacy System - Working Effectively with Legacy Code https://www.amazon.se/Working-Effectively-Legacy-Feathers-Michael/dp/0131177052/ref=asc_df_0131177052/?tag=shpngadsglede-21&linkCode=df0&hvadid=476403655867&hvpos=&hvnetw=g&hvrand=12782702779919837039&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1012432&hvtargid=pla-452008857537&psc=1&mcid=e10619ba6120358384930985d5460b0b
- Spreading ideas (bring down the fear) - Driving Technical Change https://pragprog.com/titles/trevan/driving-technical-change/
- The debt metaphor by Ward Cunningham - Debt Metaphor
- https://www.manning.com/books/architecture-modernization
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