Tackling Complexity: Practical Principles for Scaling Frontend Applications

As frontend applications grow, so does their complexity. Adding more features often brings challenges that can slow your team's productivity and introduce hidden bugs. Scaling a frontend isn't about building bigger; it's about building smarter.

This article explores core principles to keep complexity manageable as your frontend scales. We'll focus on actionable steps that can help you navigate growing codebases without losing sight of performance, maintainability, and simplicity. Some ideas here draw from an insightful piece on complexity by Frontend at Scale, and the lessons learned are applicable to anyone building large applications.

1. Keep Components Small

Components are the building blocks of any frontend. But as the codebase scales, it's easy for these building blocks to grow into unwieldy giants. The solution? Keep components small and focused.

• Single Responsibility: Each component should do one thing well.
• Avoid Long Files: Break larger components into smaller, reusable pieces.

Smaller components are easier to reason about, test, and modify. You can isolate complexity by delegating responsibilities across multiple smaller parts instead of one large, confusing unit.

2. Embrace Reusable Patterns

Reusable patterns help eliminate duplicated logic and make development faster. Think about utilities, hooks, and helper functions that can be reused across multiple components:

• Hooks (if using React) allow stateful logic to be reused easily.
• Utility Functions reduce redundancy in common data transformations.

Don't fall into the trap of copying code blocks from one component to another. Abstracting common logic into reusable functions avoids a "copy-paste" mess that can grow uncontrollably.

3. Split by Domains, Not by File Type

A lot of teams organize projects by file type components in one folder, styles in another, utilities in a third. But as the project grows, this approach can get hard to manage.

Instead, split by domain. Group everything related to a specific feature—components, styles, tests, etc.—in one place. This structure keeps related files together, making it easier to scale features and maintain a clear understanding of your application.

Example folder structure for a feature:

- Features/
  - UserProfile/
    - UserProfile.tsx
    - UserProfile.styles.ts
    - UserProfile.test.ts
    - hooks/
    - utils/

When scaling, you want to understand a feature in its entirety without jumping across folders. Domain-driven file organization helps to achieve that.

4. Apply State Management Wisely

Managing state is often one of the biggest sources of complexity in a frontend application. Introducing the wrong state management pattern too early or over-using a global state can lead to unnecessary headaches.

• Local vs. Global State: Keep state as local as possible. If multiple components don’t need access to a particular piece of state, avoid moving it to a global store.
• Split State into Layers: Use context, global state libraries (Redux, Zustand), or query libraries (React Query) depending on the state’s purpose. A data-fetching state doesn't need to live alongside UI state.

Global state management adds overhead. Assess if it’s necessary before reaching for complex solutions. Start simple and evolve as the needs of your application change.

5. Document Early, Document Often

Documentation tends to be an afterthought, but as your frontend scales, poor documentation can significantly increase onboarding time and slow down development.

• Add Inline Comments: Avoid assuming code is self-explanatory.
• Create Component Documentation: Make it easy for new developers to understand how each component works, what props it expects, and the outcomes it provides.

Even lightweight documentation can make a difference in maintaining clarity in a growing codebase.

6. Performance-First Mindset

Complexity isn’t just about code—it also shows up in how your app performs.

• Code Splitting: Split bundles to keep load times short.
• Lazy Loading: Load components and resources only when they're needed.

Performance issues multiply as features add up. Keeping performance considerations at the forefront will make sure that your app remains responsive at scale.

7. Embrace Automation

Manual processes introduce delays and increase the risk of human error.

• Code Quality: Use linters, formatters, and type checkers like ESLint and Prettier to maintain consistent quality.
• Testing: Write automated tests to catch breaking changes. As complexity grows, having a reliable test suite saves significant debugging time.

Final Thoughts

Scaling frontend applications is less about adding more features and more about managing the complexity that comes with them. As you add new capabilities, remember to:

• Keep things modular.
• Reuse as much as possible.
• Document clearly.
• Manage state effectively.

These practices keep growth in control, letting your app scale smoothly rather than turning into a tangled mess.

Many ideas here were inspired by Frontend at Scale. It's a highly recommended read for anyone building complex systems.