Taming a Large Next.js Codebase

Maintaining a large Next.js application is a constant battle against outdated dependencies, flaky tests, and bloated JavaScript and CSS bundles. These issues can slow down development and degrade the user experience. While some problems are unavoidable as a codebase grows, many can be mitigated, or even eliminated, by adopting the right tooling and architectural patterns from the start.

Type Safety With TypeScript

The first layer of defense in a large codebase is a strongly typed language like TypeScript. It enforces strictness when dealing with different data types, which helps catch potential breakages before they reach production. Next.js performs type checking by default during the next build process, but modern code editors offer real-time feedback during development.

“By default, Next.js will do type checking as part of the next build. We recommend using code editor type checking during development.”

TypeScript is especially useful during major dependency upgrades. When you update Next.js or other packages, the compiler will highlight breaking changes and type mismatches immediately, often before you even run a build. This safety net allows you to refactor with confidence, knowing that the type system will signal when an interface has shifted underneath you.

Sharing Code With a Monorepo

Building a reusable component library alongside a main application is a common goal. Architecturally, keeping the library in a separate repository feels clean, but it severely hurts the development workflow. Every change to a component requires a full build and release cycle before it can be tested within the Next.js application. When a team does this repeatedly, the time lost is significant.

Using a monorepo structure, where the component library lives alongside the Next.js application, eliminates this friction. Changes to the library are immediately available to the consumer without a separate release step. You can use a package like next-transpile-modules to allow the Next.js application to consume the library’s source code directly, bypassing the need for a build step during local development.

Several tools help manage monorepos, including Lerna, Nx, Rush, and Turborepo, as well as built-in support from yarn workspaces and npm workspaces. Lerna paired with yarn workspaces is a solid option for configuring custom build pipelines, while Nx offers a more automated, CLI-driven approach. Each tool solves slightly different problems, so the choice depends on your team’s needs.

Automating Boilerplate Generation

As more developers contribute to a large codebase, the amount of duplicated code increases. Developers often copy an existing page or component, paste it, and modify only a few parts, resulting in inconsistent variable names and accumulated technical debt. Code reviews help, but a better solution is to automate the generation of this boilerplate.

Tools like Hygen generate consistent templates for pages, components, and utility functions. This removes the temptation to copy-paste and ensures that the code entering the repository follows established patterns. If you are building Redux state logic, Redux Toolkit can similarly serve as a code generator by providing a structured way to create slices of state with less boilerplate.

Engineering Data Fetching

Fetching data from an API is straightforward with the Fetch API or Axios. However, managing the asynchronous state—cache invalidation, deduplication, and pending states—becomes a heavy burden as the application grows. Ad-hoc wrapper functions written by various developers quickly become inconsistent and difficult to maintain.

Packages like React Query and SWR provide a robust default configuration for async data fetching. They handle caching, background refetching, and performance optimizations out of the box, leaving you to manage only the essential custom behavior. Both libraries are popular, and their respective comparison guides are useful for deciding which fits your project. Zustand and XState remain alternative solutions, but React Query and SWR are currently the standard for handling server state.

Structuring and Reviewing Releases

Keeping a changelog manually is a losing battle. It is always out of date, and versioning becomes speculative. Automating this process is key to maintaining sanity. Combining Commitizen, which enforces a standard commit message format, with Semantic Release, which deduces the next version number and generates the changelog from Git commit history, is an effective strategy.

Using Husky to run these tools as hooks ensures that every commit conforms to the pattern. This enforces consistency across a team of contributors and keeps the changelog, versioning, and releases perfectly in sync, without any manual intervention. The entire process then runs automatically as code is merged and deployed.

A Visual Interface for Components

Larger applications inevitably accumulate a large collection of UI components. Without proper documentation, developers often end up building a new button simply because they didn’t know one already exists. It is also difficult to see at a glance which components are buggy or obsolete.

Storybook serves as a dedicated environment to visualize and interact with UI components in isolation. It acts as living, navigable documentation for your component library, showing what each component looks like with various props and state. This visibility helps the entire team—including designers—understand the available building blocks and the interactions they support. Coupled with a tool like Chromatic, Storybook can run automated visual regression tests during each release to catch unintended styling or behavioral changes.

Invest In Tests Early To Keep Refactoring Safe

Testing takes time, and teams shipping features on tight deadlines often skip it. That trade-off becomes expensive as the codebase grows: without tests, it’s hard to know which files a change might break, so refactoring slows to a crawl. The fix is to write tests from day one, using an approach like Test Driven Development (TDD) or whatever fits your workflow. Kent C. Dodds’ article The Testing Trophy and Testing Classifications is a good starting point for deciding which test levels matter most.

Maintainable tests give developers the confidence to refactor freely, which is essential in a large application. In practice, a solid stack is Jest for unit testing, React Testing Library for component and integration tests, and Cypress for end-to-end coverage.

Automate Dependency Updates With Dependabot

When multiple feature teams work in one repository, package versions tend to drift. Nobody wants to interrupt feature work to handle a breaking change from an upgrade, so updates get postponed—and the tech debt accumulates. Outdated packages eventually cause security vulnerabilities and performance problems.

Automating the process removes the friction. Dependabot watches for outdated packages and opens pull requests on a schedule you configure in dependabot.yml. Keeping dependencies current becomes a routine task instead of a crisis, which has proven invaluable in maintaining large Next.js applications.

Read The Production Docs Before You Deploy

One of the most useful resources for Next.js developers is the Production section of the official documentation. It lays out what you should implement before shipping to production—things that many developers otherwise guess at. Before reading it, the author admitted to making arbitrary assumptions about deployment readiness.

Browser support is a key part of that preparation. Next.js supports a wide range of browsers, but your real constraint is what your actual users run. Know your audience’s browsers before you set your build targets, not after you’ve shipped a breaking update to them.

Final Thoughts

These practices—early testing, automated dependency management, and reading the production checklist—apply to any front-end application, not just Next.js. The priority is always delivering a product that is fast, smooth, and pleasant to use. Keeping these points in mind during development has served the author well, and they’re worth adopting regardless of your stack.

Further Reading

Smashing Editorial