As an Angular developer, working with monorepos can be a powerful way to manage multiple applications and libraries in a single workspace. However, as your codebase grows, so do the build times. You might start noticing sluggish builds that drain productivity, especially in CI/CD pipelines. Slow builds don’t just hamper developer experience; they also increase feedback loops, making it harder to spot and fix issues quickly.
In this post, we’ll explore common causes of slow build times in an NX monorepo, the symptoms you might encounter, and effective solutions to optimize performance.
Common Problems with Slow Build Times
- Rebuilding Unchanged Projects
In a monorepo, even small changes to one project can trigger a build for the entire workspace. Rebuilding projects that haven't changed wastes precious time and resources. - Inefficient Task Execution
When your tasks (builds, tests, etc.) run sequentially or aren’t distributed effectively across multiple machines or cores, it results in long waits, especially on larger teams. - Overbuilding in CI/CD Pipelines
Continuous Integration environments can be particularly inefficient if they are not configured to build only the affected projects. This can lead to unnecessary builds, increasing pipeline times exponentially. - Heavy Libraries and Circular Dependencies
Another hidden cause of slow builds is the inclusion of large, rarely changing libraries in every build or the introduction of circular dependencies between projects.
Symptoms of Build Bottlenecks
- Long Feedback Loops: Changes take too long to reflect, slowing down development cycles.
- Overloaded CI Pipelines: Build times in CI environments stretch to hours, blocking release schedules.
- Developer Frustration: Team members spend more time waiting for builds than coding, leading to frustration and decreased productivity.
Optimizing NX Monorepo Build Times
Now that we’ve identified the issues, let’s look at practical techniques to tackle them.
1. Leverage Affected Commands
NX provides powerful commands like nx affected:build and nx affected:test, which focus on rebuilding only the projects impacted by code changes. This reduces the scope of builds and speeds up the process.
bashCopy codenx affected:build
By using this command, you avoid rebuilding untouched projects, shaving off minutes or even hours from the total build time.
2. Enable Local & Distributed Caching
NX’s local caching mechanism allows you to reuse build outputs from previous runs. If nothing has changed in a project, the cache will return the previous build result, bypassing the need for a full rebuild.
For even more optimization, use NX Cloud for distributed computation, enabling builds to be shared across different machines or CI pipelines.
bashCopy codenx connect-to-nx-cloud
This can cut down build times drastically, especially in multi-developer environments.
3. Parallelize Builds
NX supports parallel execution of tasks, which can significantly improve build speed by utilizing multiple CPU cores. Add the --parallel flag to your build commands to execute multiple tasks simultaneously.
bashCopy codenx build --parallel
This is particularly useful on powerful development machines or in CI/CD environments.
4. Analyze and Optimize Dependencies
Circular dependencies or heavy libraries can bottleneck your build process. Use NX’s dependency graph to visualize project relationships and eliminate unnecessary or problematic dependencies.
bashCopy codenx dep-graph
Cleaning up your project graph can reduce build complexity and speed things up.
5. Incremental Builds for Faster Compilations
Enable incremental builds by adding "incremental": true in your tsconfig.json. This allows TypeScript to store information between builds, speeding up subsequent ones.
Conclusion
Optimizing build times in an NX monorepo is essential to maintaining productivity in growing applications. By leveraging affected builds, caching, parallelization, and smart dependency management, you can dramatically cut down build times and keep your team focused on development, not waiting.
These techniques will ensure you scale your monorepo efficiently without sacrificing developer velocity.
