How do you prioritize which legacy code to refactor first?

Start by assessing the legacy codebase to identify areas with the highest technical debt, focusing on code that is prone to bugs, difficult to maintain, or hinders new feature development. Using static code analysis tools, measure code complexity, code smells and dependency issues. Evaluate how changes to specific code modules will affect the overall system. This involves examining the code's criticality to business operations, its usage frequency, and performance bottlenecks. Additionally, consider the potential for improvement in terms of security, and scalability. Collaborating with cross-functional teams to gather insights on pain points, functional and technical bottleneck to prioritize refactoring efforts.

I have a rather unique take on legacy code: I don't believe bugs, security or scalability are the main issues. It all comes down to prioritisation and risk management. You need to be aware of the current state of your system though (SAST, dependency analysis, etc...) I believe the real problem of legacy code is the impact it has on the ability to delivery working software in the least amount of time. That's what you need to measure: On which subsystem my team takes the most time? Then it all comes back to prioritisation: - Invest on the future and take time to refactor now? - Deliver now but impede future developments? My rule of thumb: Be a boy scoot & Leave the place cleaner than when you found it. Not perfect, just a bit better.

In the intricate process of code refactoring, the initial step involves a meticulous impact analysis to make informed decisions. Understanding the ripple effects of code changes on both the system and its users is paramount. This multifaceted evaluation considers various dimensions, helping developers discern which sections of code warrant immediate attention. In my opinion, this is always a very critical point. The better the impact analysis, the fewer errors and problems will arise later. In my experience, there will always be problems, but it's important to reduce them as much as possible.

To effectively prioritise which code to refactor first, I suggest reviewing the portions of the code that will need to change when starting a new project, feature or complex bug fix. Identify the difficult-to-modify sections that are overly complex or generally intimidating. The goal is to pinpoint the smallest scope that, once refactored, will enable safe integration of your planned changes. By addressing these challenges proactively, you ensure a smoother development process and enhance the overall quality and longevity of the codebase.

Maintaining leagacy code is challenging for eveyone in our Industry. - Focus on critical codebase and invest time on upgrading/updating to the latest technology to avoid surprises in long run. - Understand the complexity and engage set of teams to divide the work and come up with the solutions. - Getting Legacy code/technology experts are challenging sometimes, so its better to move ahead with the investing time in revamping it instead of letting it run as it is. - Cost to support such code systems is major aspects to consider. If you can replace the legacy code with latest one, it's cost saving.

Embarking on code refactoring is like navigating uncharted waters. The second crucial step involves a risk assessment, gauging potential pitfalls in altering existing code. Delving into uncertainties enables informed decisions, balancing innovation with codebase stability. To mitigate risks, consider leveraging tools like unit testing frameworks for systematic validation, catching regressions. Code reviews offer collaborative scrutiny before merging changes, and version control systems allow swift rollbacks if needed.

There are 2 ways to run an impact analysis exercise prior to refactoring. 1. "Tactical" approach In which you consider the services that are impacting your business the most due to poor performance or scalability issues .. for example services that causes downtime or DB failures at high traffic such as Identity or Payment processing. 2. "Strategic" approach In which you'd consider refactoring services that can cause security concerns in the future, or services that are poorly written, heavily coupled and degrades the overall throughput of the development team. A wise leader usually considers sorting out the most immediate business needs first while partnering with business counterparts to create long-term refactoring plans.

The most important factors in performing true risk assessment are these. - What is our appetite for risk. If we have a healthy appetite for risk then mitigating risks to zero is a low value activity. - what controls could we deploy to mitigate the risk (is refactoring the only option) - If we benchmark the risk at level A1 without controls, and realise that it becomes a C4 with controls, is that good enough

The definition of risk might vary, but one that works the best for me is complexity x churn x existing knowledge in the org x seniority of the current team.

Should you dive into refactoring legacy code or let sleeping dogs lie? ???? Imagine you're on a ship navigating through a sea of legacy code. The second step is to assess the risk of refactoring. Ask yourself: → How confident are you that you can refactor without breaking anything? → Is the code well-tested? → How easy is it to isolate and revert changes? Tools like unit testing, code reviews, and version control are your compass and map. They help reduce risk and ensure code quality. But is it worth the time and effort, or should you chart a different course? ???

The third step in the code refactoring process involves a comprehensive evaluation of the potential value gained from the proposed changes. This step is pivotal in justifying the investment of time and resources into refactoring efforts. The following aspects should be considered during the value estimation: - User Experience and Satisfaction - Cost Savings - Security Enhancement - Maintainability and Code Quality - Performance Improvement - Value Estimation

According to system theory, refactoring code that isn't a bottleneck is useless. So, refactoring efforts should focus only on bottlenecked areas. Often, we see that specific code sections block new features or cause most of the significant reliability, security, or performance issues. In such cases, assessing the scope, cost, and timeline of refactoring these sections is crucial. A separate refactoring project may be necessary if the required refactoring is extensive and cannot be integrated with ongoing feature work. Alternatively, the feature implementation may need to be postponed for strategic alignment.

It's vital to grasp the nature of your technical debt, comprehend how its components interlink, and identify the sequence in which changes must occur. However, when estimating value, it's beneficial to tie code refactoring to specific features when feasible. By connecting it to business needs, the refactoring not only becomes easier to advocate for but also aids in its prioritization in subsequent steps.

Always ask is this going to make our users better off than any other alternative? One point that is missing from the mentioned examples is developer experience. Often refactoring makes the code easier to work with going forward - abstracting things now might cost a week of time but will save you multiple weeks in the near future = no brainer! Even in that case you are taking the user's perspective. If I invest 1 week to have 3 additional weeks of dev time over next 6 months the users will benefit ultimately.

Code refactoring process involves the use of a prioritization matrix to systematically rank the code that requires refactoring. This step ensures that resources are allocated efficiently and that the most impactful and valuable changes are addressed first. The prioritization matrix typically considers impact, risk, and value criteria. Identify the code segments that fall into the high-impact, low-risk, and high-value quadrant of the matrix as top priority candidates for refactoring. These are areas where improvements are likely to yield substantial benefits with minimal associated risks.

Applying a simple prioritization method may not suffice for intricate tasks such as refactoring old code. Consider these key factors for a more effective approach: - Identify Impact Areas: Determine if refactoring affects performance or user experience. -Technical Debt Assessment: Evaluate the complexity and skills needed for refactoring. -Future Development Alignment: Ensure refactoring aligns with upcoming projects and business goals. -Game Performance: Prioritize improvements in game stability and efficiency. Engage a cross-functional team for diverse insights, balancing technical, creative, and business needs in the prioritization process.

Refactoring is not just a technical task; it's a strategic and communicative endeavor. When creating a refactoring plan, it's crucial to view it as a collaborative effort that involves not only the technical team but also various stakeholders. Effective communication is key to gaining support and understanding for the refactoring process. Consider the perspective of your team members, managers, clients, and users. From the team's viewpoint, emphasize the long-term benefits of refactoring in terms of code maintainability, reduced technical debt, and improved development efficiency. Highlight how the refactoring aligns with the overall project goals and contributes to a healthier and more sustainable codebase.

When prioritizing legacy code for refactoring, it is important to focus on areas that directly impact performance, scalability, or ongoing product goals. In my experience leading platform transformations, I prioritized refactoring efforts by identifying high traffic modules or areas of the codebase that posed the greatest risks to system stability. Once prioritized, I worked with my teams to create a clear refactoring plan outlining the scope, goals, timeline, and expected outcomes. Transparent communication with stakeholders was critical to setting expectations and maintaining buy-in throughout the refactoring process. This approach allowed my teams to systematically refactor key components without disrupting ongoing operations.

When refactoring code, it's essential to ensure it's covered by automated tests from the outset. If the code lacks test coverage, begin with minimal "unsafe" refactoring to enable testing, then proceed to write the necessary tests. Once the code is testable, adopt a cautious approach by refactoring in small, reversible steps that allow you to revert changes quickly if tests fail. Regular committing and deploying are essential to maintain a continuous deployable state and prevent the accumulation of changes that could lead to deployment issues. In some cases, duplicating code and using feature flags may be necessary to safely test changes in production and easily revert to the original code if needed.

The first step is to ask and understand is WHY you are refactoring? You might identify tech debt or monolith architecture, but in what way are these affecting the business? For example, are features taking too long to deliver, or is integration with other services almost impossible? You must understand the business impact and reason for refactoring. Then you can evaluate impact, risk, and value to guide the type of refactoring and prioritisation. Ultimately, you need ensure the refactoring aligns with broader strategic business goals.

We should consider below factors 1.Business Impact: Refactor code that directly affects critical business processes or customer experience. 2.Technical Debt: Prioritize code that is difficult to understand, maintain, or extend. 3.Dependencies: Focus on code that has high dependencies and impacts other components. 4.Testability: Give priority to code with low test coverage or lacking proper unit tests. 5.Cost-Benefit Analysis: Evaluate effort vs. potential benefits for each refactoring opportunity. 6.User Feedback: Address user-reported issues & frequently encountered bugs. 7.Development Velocity: Target code that hinders development speed and agility. Prioritize refactoring the payment processing module that impacts customer transactions.