Common Problems with Next.js App Router (Real-World Experience) | Diffcozen

The Next.js App Router is a powerful evolution of the framework, introducing React Server Components, improved routing, layouts, and modern data-fetching patterns.
However, most tutorials focus only on its benefits. In real-world projects, developers often face challenges that are rarely discussed.

In this article by Diffcozen, we’ll explore the hidden problems of the Next.js App Router, based on practical development experience, and share solutions you can apply in production-ready applications.

1. The Learning Curve Is Steeper Than Expected

For developers coming from the Pages Router or traditional React apps, the App Router can feel overwhelming.

Common Confusions:

• Server Components vs Client Components

• When and why to use "use client"

• New data-fetching and caching behavior

• File-based routing logic

The problem:
The official documentation is solid, but real-world examples are limited.

Diffcozen’s recommendation:
Start with small demo projects. Treat Server Components as the default and only use Client Components when necessary.

2. Mixing Server and Client Components Can Hurt Performance

Server Components are one of the biggest strengths of the App Router—but misusing Client Components can quickly reduce performance.

Hidden Issues:

• Unnecessary JavaScript sent to the browser

• Increased bundle size

• Unexpected hydration problems

The problem:
Many developers mark entire components as client-side just to “make things work.”

Solution:
At Diffcozen, we recommend keeping components server-first and isolating client logic only where interaction is required (forms, modals, animations).

3. Data Fetching Seems Simple—Until Caching Gets in the Way

The built-in fetch() API in the App Router includes powerful caching by default, which can be confusing.

Real-World Problems:

• Stale data appearing unexpectedly

• Difficulty invalidating cached responses

• Dynamic pages behaving like static ones

The problem:
Developers often don’t realize that data is cached automatically.

Solution:
Understand caching options like cache: 'no-store' and revalidate. At Diffcozen, we emphasize consciously choosing between static, dynamic, and revalidated data.

4. Debugging Is Harder Than in Pages Router

Error handling in the App Router can be frustrating, especially in large applications.

Common Challenges:

• Unclear error messages

• Mixed server-side and client-side stack traces

• Bugs that appear only in production

Solution:
Use proper error boundaries, check both server and browser logs, and always test production builds locally—an approach we strongly follow at Diffcozen.

5. Folder Structure Becomes Messy in Large Projects

While file-based routing is great for small apps, large Next.js projects can quickly become difficult to manage.

Problems:

• Deeply nested folders

• Confusion between routes and components

• Hard onboarding for new developers

Best Practice:
At Diffcozen, we separate reusable components, features, and route-specific logic to keep large applications scalable and maintainable.

6. Third-Party Libraries Aren’t Always App Router-Ready

Many popular libraries still assume a client-only environment.

Common Issues:

• Libraries breaking during SSR

• Runtime errors in production

• Poor compatibility with Server Components

Solution:
Before adding any dependency, check its SSR support. Use dynamic imports and isolate client-only code when necessary.

7. App Router Isn’t Always the Right Choice

Despite its power, the App Router isn’t mandatory for every project.

The truth:
Simple dashboards, landing pages, or small apps may still work perfectly with the Pages Router.

Diffcozen’s advice:
Choose the architecture based on project needs—not trends.

Conclusion

The Next.js App Router represents the future of the framework, but it’s not without limitations.

To build successful production apps, developers must:

• Understand Server vs Client Components

• Control data fetching and caching behavior

• Design a clean project structure

• Test and debug carefully

At Diffcozen, we focus on teaching modern development with a real-world, production-first mindset, helping developers build Next.js applications that are scalable, performant, and maintainable.