When Using Solid Principles May Not Be Appropriate

1. Introduction

SOLID principles help us build flexible and module software and keep our code maintainable and scalable.

However, sticking to SOLID isn’t always the best approach. Applying these principles can sometimes make our code more complex than necessary. Instead of improving maintainability, following them can slow down development and even hurt performance.

In this tutorial, we’ll explore the cases when following SOLID principles isn’t the right choice. We’ll look at real-world scenarios where strict adherence can lead to over-engineering and inefficiency.

2. Overview

SOLID consists of five core principles that guide object-oriented design:

While these principles promote clean and modular code, they aren’t always necessary.

3. Scenarios Where SOLID May Not Be Necessary

3.1. One-Off or Short-Lived Projects

Not all software needs long-term maintenance. Some projects serve a single purpose and won’t need future modifications or extensions, so applying SOLID in these cases can be overkill.

For example, suppose we’re writing a one-time data migration script to extract and transform data for an enterprise resource planning (ERP) migration. In that case, we don’t need to focus on reusability or extensibility. A simple, procedural approach may be more efficient, as the code will be easier to write and execute without unnecessary abstractions.

3.2. Performance-Critical Applications

While abstraction improves maintainability, it can also introduce performance costs. In real-time systems, such as embedded software, high-frequency trading platforms, or low-latency applications, enforcing SOLID can lead to unnecessary indirection and performance bottlenecks.

The OCP principle encourages extending behavior through inheritance or interfaces rather than modifying existing code. However, excessive use of polymorphism can slow down execution. Similarly, the DIP principle often leads to dependency injection frameworks, which can increase startup times and reduce efficiency.

In these cases, minimizing abstraction and reducing the number of function calls optimizes performance without sacrificing maintainability.

3.3. Small, Self-Contained Applications

If an application is small and serves a limited purpose, over-engineering with SOLID can make it unnecessarily complex. A simple script that performs a well-defined task doesn’t need multiple layers of abstraction.

For example, a daily file backup script that moves files to a secure storage location doesn’t need a complex class hierarchy. A single function may be enough to handle the task efficiently.

When small and easily understood code does the job, we don’t need to make it more complex just for the sake of following design principles.

3.4. Games and Rapid Prototyping

Game development and prototyping often require fast iteration cycles. While core game engines and frameworks may follow SOLID principles, the game logic itself is often written quickly and discarded after a project ends.

For example, applying strict interface segregation to game mechanics may result in too many loosely connected components, making it harder to quickly tweak or replace core functionality. Instead of modifying a simple movement system, developers may need to adjust multiple interfaces and dependency-injected modules, which can increase development time rather than reduce it.

3.5. Highly Dynamic Environments

Startups and fast-moving teams often work in environments where requirements change frequently. In such cases, designing a system with extensibility in mind may not be beneficial because the core requirements are still evolving.

For example, a startup iterating quickly on an MVP  (minimum viable product) may find that strict adherence to the OCP principle leads to excessive abstraction that needs constant refactoring. Instead of optimizing for future changes, it’s often better to focus on delivering a working solution quickly and refactor later when the system stabilizes.

Keeping the codebase simple and adaptable is often more important than following SOLID when the business direction is unclear.

3.6. When the Cost of Abstraction Outweighs the Benefits

While abstraction makes code more modular, too much abstraction can reduce readability and maintainability. If applying SOLID principles makes the code harder to follow, it might be better to simplify the design.

For example, a simple create, read, update, delete (CRUD) application that manages user data doesn’t necessarily need a complex set of interfaces. Excessive abstraction may increase the learning curve for new developers and make debugging harder.

If a design decision adds more complexity than clarity, it’s worth questioning whether SOLID is the right approach.

4. Common Pitfalls of Overusing SOLID

When we apply SOLID principles without considering the context, it can lead to unnecessary complexity. Overusing these principles can make the code harder to understand, maintain, and even work against the intended benefits:

Let’s take a look at each of these issues in more detail.

4.1. Over-Fragmentation from SRP

The SRP encourages small, focused classes. While separating concerns improves modularity, breaking down functionality into too many micro-classes can make debugging harder.

Imagine a UserService class that handles user profile management. Splitting it into separate classes for authentication, profile updates, and settings will introduce unnecessary complexity:

4.2. Unnecessary Abstraction from OCP

The OCP principle promotes extensibility, but forcing abstraction too early can introduce complex class hierarchies that don’t provide real value.

For example, in an overengineered approach, instead of a simple calculateDiscount() method in a product cart class, we’ll use an abstract method to allow for various discount algorithms. However, if the discount logic rarely changes, this abstraction adds unnecessary layers that complicate maintenance.

4.3. Forced Inheritance from LSP

Another issue is rigid inheritance from LSP. If a subclass violates real-world behavior, inheritance can become problematic.

For example, forcing all birds to inherit a fly() method leads to awkward designs where non-flying birds like penguins must override the method. In such cases, composition is often a better alternative.

4.4. Interface Explosion from ISP

The ISP principle can also be misapplied, leading to interface explosion.

While ISP encourages smaller interfaces, breaking them down too much can create unnecessary complexity, similar to SRP overuse.

4.5. Overuse of Dependency Injection from DIP

Overusing the DIP principle can introduce unnecessary dependency injection (DI) frameworks that slow down applications.

In small projects, enforcing DI across all components adds complexity without adding much flexibility. Manually injecting dependencies or using simple factories is often a more efficient alternative.

5. Striking the Right Balance

The biggest risk of overusing SOLID is reduced readability. If a simple functionality requires navigating multiple abstract classes, interfaces, and dependency injections, the code becomes hard to follow rather than easy to maintain.

Instead of treating SOLID as a strict rulebook, we should use it as a guideline and apply it where it makes sense and relax it when simplicity is more beneficial:

While SOLID provides an excellent foundation for writing scalable software, applying it without considering the project’s needs can lead to over-engineering. Instead of enforcing abstraction or separation by default, we should focus on keeping the code clean, simple, and adaptable. The best approach is to apply SOLID when it adds value, not when it complicates rather than simplifies the design.

If updating a simple functionality requires navigating through multiple abstract classes, interfaces, and DI configurations, the code is likely over-engineered. SOLID should improve clarity, not make it harder to follow.

6. Conclusion

In this article, we explored the cases in which following SOLID principles isn’t appropriate. While SOLID helps us write maintainable, scalable, and flexible software, strict adherence isn’t always the best approach. Sometimes, it can introduce unnecessary complexity, reduce performance, or slow development.

For example, SOLID isn’t a good fit for short-lived scripts, performance-critical applications, and rapidly evolving projects. The common pitfalls of overusing SOLID include excessive abstraction, over-fragmentation, and rigid inheritance structures.

Instead of treating SOLID as a strict rulebook, we should apply it where it adds value. In large, evolving codebases, it can help prevent technical debt and improve maintainability. However, in simpler or highly dynamic projects, keeping the design straightforward and prioritizing readability often leads to better results.