How can you manage technical debt when adopting domain-driven design?

1 What is technical debt?

Technical debt is a metaphor that compares software development to financial debt, with the idea that taking shortcuts or using workarounds can help you deliver a feature or fix faster, but can also create problems and costs in the future. Technical debt can be intentional or unintentional and can have various sources, such as lack of time, resources, or skills; changing requirements or expectations; poor design or architecture decisions; inconsistent coding standards or tools; legacy code; and bugs or errors. The negative impacts of technical debt on a software project can include lower quality, reliability, or security; higher complexity, coupling, or redundancy; reduced performance, scalability, or usability; increased maintenance, testing, or debugging efforts; and reduced productivity, innovation, or agility.

2 How does DDD relate to technical debt?

DDD is a software design approach that can help you avoid or minimize technical debt, such as misalignment between the software and the business domain, ambiguity or inconsistency in the domain language or concepts, lack of modularity, cohesion, or encapsulation in the code structure, and difficulty in adapting to changing business needs or opportunities. By applying DDD principles and practices, such as using a ubiquitous language to define and communicate the domain terms and rules, creating bounded contexts to isolate and integrate different subdomains and models, designing domain entities, value objects, aggregates, services, and repositories to represent and manipulate the domain concepts and behaviors, implementing domain events, sagas, and event sourcing to capture and propagate the domain changes and history, and applying strategic patterns like context mapping, anti-corruption layer, or open host service to manage dependencies and interactions between bounded contexts you can achieve a software design that is more expressive, consistent, maintainable, evolvable and accurately reflects the business domain.

3 How can you manage technical debt when adopting DDD?

Adopting DDD is not a foolproof solution for eliminating technical debt from your software project; in fact, it can introduce its own challenges and risks that can contribute to technical debt. To manage technical debt when adopting DDD, you should take a balanced and pragmatic approach that considers the trade-offs and benefits of each design decision. Assessing the value and feasibility of DDD for your project and domain, choosing the right scope of DDD, focusing on core subdomains and models, collaborating with domain experts and stakeholders, refactoring and improving code and models continuously, documenting design decisions and actions, and measuring the impact of technical debt are all strategies that can help you manage technical debt when adopting DDD.

4 What are some examples of technical debt in DDD?

To illustrate how technical debt can arise and be managed in DDD, here are some examples of common scenarios and solutions. For instance, an anti-corruption layer can be used to isolate and protect a new DDD system from a legacy system, while context mapping can be used to identify and analyze relationships between bounded contexts. Additionally, domain events and event sourcing can be used to capture and store domain changes, while sagas can coordinate and execute domain transactions and workflows. By implementing these solutions, you can avoid or reduce the technical debt caused by the legacy system's complexity or inconsistency, as well as enhance the modularity, cohesion, scalability, and flexibility of your code.

5 What are some best practices for managing technical debt in DDD?

To conclude, managing technical debt in DDD requires being aware and proactive in recognizing and acknowledging the technical debt, and planning and prioritizing its prevention, reduction, or repayment. It is also important to be pragmatic and balanced when considering the trade-offs and benefits of each design decision, and using DDD where it adds value. Additionally, it is essential to be collaborative and iterative by involving domain experts and stakeholders, as well as refining and validating code and models regularly. Moreover, it is essential to be continuous and consistent when applying and following DDD principles, refactoring code, and improving models. Finally, it is necessary to be transparent and accountable by documenting design decisions, communicating actions taken, measuring the impact of those actions, and monitoring their cost on the project.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?