CI/CD Cost Optimization: Runner Sizing, Caching ROI, Spot Instances, and Build Minute Economics

CI/CD Cost Optimization#

CI/CD costs grow quietly. A team of ten pushing five times a day, running a 15-minute pipeline on 4-core runners, burns through 2,500 build minutes per week. On GitHub Actions at $0.008/minute for Linux runners, that is $20/week. Scale to fifty developers with integration tests, matrix builds, and nightly jobs, and you are looking at $500-$2,000/month before anyone notices.

The fix is not running fewer tests or skipping builds. It is eliminating waste: jobs that use more compute than they need, caches that are never restored, full builds triggered by README changes, and runners sitting idle between jobs.

Self-Hosted CI Runners at Scale: GitHub Actions Runner Controller, GitLab Runners on K8s, and Autoscaling

Self-Hosted CI Runners at Scale#

GitHub-hosted and GitLab SaaS runners work until they do not. You hit limits when you need private network access to deploy to internal infrastructure, specific hardware like GPUs or ARM64 machines, compliance requirements that prohibit running code on shared infrastructure, or cost control when you are burning thousands of dollars per month on hosted runner minutes.

Self-hosted runners solve these problems but introduce operational complexity: you now own runner provisioning, scaling, security, image updates, and cost management.