Software Engineering

Demand Composition: Designing Software That Scales and Evolves

In modern software engineering, building applications that are modular, maintainable, and scalable isn’t just a best practice—it’s a necessity. Enter the concept of Demand Composition, a mindset that prioritizes single-purpose abstractions, composable modules, and clear documentation to future-proof your codebase.

This article dives deep into the principles and considerations behind Demand Composition, highlighting its practical impact on real-world software systems.

The Core Principles of Demand Composition

1️⃣ Single-Purpose and Replaceable Abstractions

At the heart of Demand Composition is the idea that every abstraction should do one thing—and do it well. Whether it’s a function, class, or entire package, its purpose should be clear, focused, and limited. This clarity ensures that if requirements change or a module becomes obsolete, it can be replaced or removed without a ripple effect across the system.

Example: If you’re writing a data access layer, separate the query construction from the connection handling. This way, if your database backend changes, you can swap out the connection module without rewriting query logic.

2️⃣ Composable Modules: Easy to Add, Easy to Remove

A composable module should fit into an application like a LEGO brick, seamlessly plugging into or detaching from the broader system. To achieve this:

Keep dependencies minimal and explicit.
Define clean, well-documented interfaces.
Avoid hardcoded connections between unrelated parts.

This not only improves maintainability but also supports incremental evolution—you can experiment with new features by adding or replacing modules without breaking existing functionality.

3️⃣ Packages Must Be Independently Useful and Well-Documented

Every package should be valuable on its own, with comprehensive documentation that covers:

Its purpose and responsibilities.
How to integrate it into larger systems.
Any dependencies or configuration it requires.
Clear examples and use cases.

This ensures that anyone (including future-you) can pick up the module and understand its role without digging through unrelated code.

4️⃣ New Features Should Start as New Packages

When adding new features, resist the temptation to cram them into existing packages. Instead:

Start by building a new package.
Evaluate whether the feature can exist independently.
If not, refactor the existing codebase to isolate responsibilities and make room for the new module.

This strategy minimizes technical debt and encourages continuous refinement of the system’s architecture.

5️⃣ Cohesion vs. Coupling: Know When to Combine Modules

Not all abstractions benefit from being split apart. If two modules are so tightly coupled that they always change together—and those changes are bidirectional—it may make sense to merge them into the same package. This decision:

Reduces the risk of introducing inconsistent behavior.
Simplifies versioning and deployment.
Enhances internal cohesion, which improves readability and maintainability.

🌟 Additional Considerations

While the core principles are essential, there are a few additional points worth integrating into your Demand Composition approach:

🔹 Explicit Boundaries

Clearly define the boundaries of each module or package. Avoid “leaky abstractions” where internal implementation details become visible outside the module. This prevents accidental misuse and simplifies refactoring.

🔹 Version Control and Dependency Management

Use semantic versioning and strict dependency declarations to manage inter-package relationships. This approach ensures changes in one module don’t unexpectedly break dependent systems.

🔹 Testing in Isolation

Every module should be tested independently. This reinforces its composability and helps catch issues early, especially when modules are reused across different projects or teams.

🔹 Monitoring Usage Patterns

Track how often each module is used and how frequently it changes. Modules that rarely change but are used widely should be kept stable, while modules that change frequently might need closer scrutiny for opportunities to refactor or decouple.

🏗 The Payoff: Scalable, Maintainable Systems

Embracing Demand Composition isn’t just about clean code—it’s about building systems that scale with your needs. By designing single-purpose, composable, and well-documented modules, you’re setting up your project for:

Easier feature development.
Lower maintenance overhead.
Faster onboarding for new developers.
Smoother adaptation to changing requirements.

🚀 Finally

Demand Composition is about respecting the boundaries of your code. It’s about deliberately designing modules that not only serve today’s needs but can also evolve and adapt as the system grows. The result? Software that’s not only robust but also flexible enough to thrive in the ever-changing landscape of technology.