Optimize Bazel builds for large-scale monorepos

Bazel Build Optimization

Production patterns for Bazel in large-scale monorepos.

When to Use This Skill

• Setting up Bazel for monorepos
• Configuring remote caching/execution
• Optimizing build times
• Writing custom Bazel rules
• Debugging build issues
• Migrating to Bazel

Core Concepts

1. Bazel Architecture

workspace/
├── WORKSPACE.bazel       # External dependencies
├── .bazelrc              # Build configurations
├── .bazelversion         # Bazel version
├── BUILD.bazel           # Root build file
├── apps/
│   └── web/
│       └── BUILD.bazel
├── libs/
│   └── utils/
│       └── BUILD.bazel
└── tools/
    └── bazel/
        └── rules/

2. Key Concepts

Concept	Description
Target	Buildable unit (library, binary, test)
Package	Directory with BUILD file
Label	Target identifier //path/to:target
Rule	Defines how to build a target
Aspect	Cross-cutting build behavior

Templates and detailed worked examples

Full template library and detailed worked examples live in references/details.md. Read that file when you need the concrete templates.

Best Practices

Do's

• Use fine-grained targets - Better caching
• Pin dependencies - Reproducible builds
• Enable remote caching - Share build artifacts
• Use visibility wisely - Enforce architecture
• Write BUILD files per directory - Standard convention

Don'ts

• Don't use glob for deps - Explicit is better
• Don't commit bazel-* dirs - Add to .gitignore
• Don't skip WORKSPACE setup - Foundation of build
• Don't ignore build warnings - Technical debt