TypeScript Performance Tips for Large Repos

Large TypeScript repositories have become a mainstay in professional development environments. As codebases grow in size and complexity, maintaining optimal TypeScript performance becomes increasingly challenging. Without deliberate tuning and best practices, developers may experience long compile times, sluggish editor responsiveness, and general productivity bottlenecks. This article outlines proven strategies and tips to improve TypeScript performance specifically in the context of large repositories, ensuring speed and scalability without compromising on type safety or tooling experience.

1. Use Project References

One of the most effective ways to scale TypeScript in large codebases is to modularize the code using Project References. Introduced in TypeScript 3.0, project references allow you to break up your monolithic codebase into smaller units that can be built and type-checked independently.

This technique offers the following benefits:

  • Incremental builds: TypeScript only rebuilds projects that have changed or have dependencies that changed.
  • Improved editor performance: Editors like VSCode are more responsive when they deal with smaller projects.
  • Cleaner architecture: Enforces separation of concerns and dependency boundaries.

To implement project references, create individual tsconfig.json files for each module and reference them from a top-level config:

{
  "files": [],
  "references": [
    { "path": "./packages/module-a" },
    { "path": "./packages/module-b" }
  ]
}

2. Enable Incremental Compilation

Large repositories often benefit from incremental compilation. By enabling the incremental option in your tsconfig.json, TypeScript saves information about your project graph to disk so that subsequent builds are faster.

{
  "compilerOptions": {
    "incremental": true
  }
}

This feature significantly reduces compilation time during active development by avoiding full recompilation unnecessarily. It works especially well in combination with project references.

3. Tune Your tsconfig.json

Your configuration file plays a critical role in TypeScript performance. Various compiler options can help ease the burden on type checking and emit. Here are some recommended tweaks:

  • Set “skipLibCheck”: true – Skips type-checking of definition files inside node_modules. Speeds up compilation without affecting correctness for most use cases.
  • Use “noEmit”: true during development
  • Minimize “include” and “files” – Avoid wildcard globs like "src//*" and prefer listing only the necessary entry points.

Example:

{
  "compilerOptions": {
    "skipLibCheck": true,
    "noEmit": true,
    "target": "ES2020",
    "module": "ESNext"
  },
  "include": ["src/index.ts"]
}

Being explicit reduces the amount of code the compiler has to watch and process, especially important in repositories with many unrelated files.

4. Avoid Complex Type Expressions

Types themselves can also severely impact performance. Overly complex or deeply recursive type definitions may lead to excessive compilation times or even out-of-memory exceptions.

Watch out for:

  • Recursively defined types
  • Massively overloaded function types
  • Union types with dozens of variants
  • Mapped types over large objects

If you notice the compiler slowing down after introducing a specific type, it’s worth evaluating whether a simpler alternative could provide a similar benefit with better performance.

5. Leverage Type-Only Imports

To minimize bundling complexity, compilation effort, and ensure clean dependency graphs, use import type for importing types only. This helps TypeScript optimize module resolution and type analysis.

import type { User } from './models/User';

This small change can improve performance and clarity, especially in repositories with hundreds of type imports spread across the codebase.

6. Limit the Use of “any” During Development

While any may seem like a quick way to circumvent typing issues, over-reliance on it can backfire in structural type systems like TypeScript’s. Excessive use of any often leads to hidden type-checking pitfalls and make future refactors harder — ultimately leading to slower performance due to insufficient type information.

If you must use it temporarily, isolate it clearly and plan to replace it with better types later. Prefer unknown as a safer, more restrictive alternative when working with uncertain data.

7. Use Watch Mode Efficiently

When working with a large repo in development, running tsc --watch can be slower if all files are included. To speed this up:

  • Make sure files not actively being modified are moved into separate projects and referenced
  • Use --incremental together with --watch
  • Run partial builds for specific modules, not the whole repo

Also consider using tsc -b for building only the projects you care about. This builds only impacted projects based on what has changed since the last build.

8. Use a Performance Monitoring Tool

To identify what’s slowing down your TypeScript builds or editor performance, use the built-in TypeScript performance tracing and logging features.

  • Pass --generateTrace traces to tsc to produce a trace file readable in Chrome profiler
  • Use VSCode’s integrated performance tools to detect which files or projects are slowing intellisense
  • Use ts-essentials to refactor bloated or redundant types

9. Keep Dependencies Lean

Each dependency you include in your TypeScript project brings along its own type declarations. Some community packages ship poorly written or bloated types that can slow down the compiler significantly. Regularly prune unused dependencies and audit the type definitions of those you rely on most heavily.

It’s good practice to:

  • Prefer dependencies with active maintenance and type safety in mind
  • Use npm dedupe to reduce nested packages and avoid duplicate type trees
  • Manually inspect problematic d.ts files if your IDE slows down when importing them

10. Consider Using TS Server Plugins Wisely

VSCode and other editors using the TypeScript Language Server (TS Server) often support performance-enhancing plugins. While they can speed up certain workflows or add productivity features, too many plugins (or poorly designed ones) can also slow things down.

Evaluate your extensions periodically and disable ones that aren’t essential. Particularly if you notice editor slowness, try running in safe mode or disabling extensions temporarily to pinpoint the source.

Conclusion

Large TypeScript repositories don’t have to become a burden. With the right performance strategies — such as leveraging project references, configuring tsconfig appropriately, taming complex types, and auditing imports — you can maintain a scalable, smooth development experience. TypeScript itself continues to evolve with features that favor big codebases, but it’s up to engineers to apply these capabilities thoughtfully to get the most out of them.

By treating performance as an ongoing part of your TypeScript architecture, you’ll not only reduce build times and improve IDE responsiveness, but also ensure that your team can continue iterating quickly and confidently at scale.