Problem Statement
Why is dependency caching important in CI/CD pipelines?
Explanation
Dependency caching stores downloaded dependencies (Maven .m2, npm node_modules, pip cache) between pipeline runs, significantly reducing build time by avoiding re-downloading unchanged dependencies. Without caching, each build downloads all dependencies from scratch, wasting time and bandwidth.
Caching strategies: use lock files (package-lock.json, Gemfile.lock, yarn.lock) as cache keys - cache invalidates only when dependencies change. Example GitLab:
```yaml
cache:
key:
files:
- package-lock.json
paths:
- node_modules/
```
GitHub Actions:
```yaml
- uses: actions/setup-node@v3
with:
node-version: '18'
cache: 'npm'
```
Best practices: cache by lock file hash, separate cache per branch/project, set reasonable cache expiration, cache both dependencies and build outputs when possible, use shared cache storage (S3, GCS) for distributed runners. Benefits include faster builds (30-80% reduction in build time), reduced network usage, more reliable builds (less dependent on external registry availability). Understanding caching is essential for optimizing pipeline performance.
