AWS CodeBuild
Fully managed build service that compiles code, runs tests, and produces deploy-ready artifacts — no build servers to manage.
Verified against AWS documentation · 2026-08-28
Key facts
- 01Serverless CI: you don't provision, patch, or scale build servers — builds run in fresh, ephemeral containers that are thrown away after every run
- 02buildspec.yml defines the build — phases (install, pre_build, build, post_build), commands, environment variables, and artifact output, living in the repo root
- 03Sources: GitHub, GitHub Enterprise, Bitbucket, CodeCommit, or S3; artifacts typically land in S3 or ECR (Docker images)
- 04Scales automatically and runs builds concurrently — no build queue when traffic spikes, unlike a single Jenkins box
- 05Can run inside your VPC to reach private resources (internal RDS for integration tests, private package repos)
Exam triggers
Phrases and scenarios that point here.
- "Compile", "run unit tests", "produce build artifacts", "no servers to manage for CI"
- Jenkins maintenance pain / build server patching → replace with CodeBuild
- Build stage inside a CodePipeline pipeline → the build action is CodeBuild
- Build needs access to resources in a private subnet → CodeBuild with VPC configuration
- Build Docker images and push to ECR → CodeBuild with privileged mode
Not this service
- Orchestrating the whole release flow (source → build → deploy stages) → CodePipeline
- Deploying artifacts to EC2, Lambda, or ECS → CodeDeploy
- Full platform that builds AND runs the app for you → Elastic Beanstalk
Use cases
- 01Replacing a self-managed Jenkins server — the classic 'our build box died on release day' problem disappears because every build gets a fresh managed environment
- 02Building and pushing Docker images to ECR as part of a container deployment pipeline
- 03Running the test suite on every pull request via webhook, so broken code is caught before merge instead of after deploy
- 04Integration tests against a private database — CodeBuild joins the VPC, hits the internal RDS endpoint, no public exposure needed
- 05Monorepo teams running many concurrent builds — CodeBuild parallelizes instead of queueing like a fixed-size build server would
How it's charged
- 01Pay per build duration — EC2 compute is billed per minute (rounded up), Lambda compute per second, so a 10-second build on EC2 still costs a full minute
- 02Rate depends on compute type: bigger instances (more vCPU/memory) and Windows cost more per minute; ARM (Graviton) is meaningfully cheaper than x86
- 03No charge when nothing is building — no idle cost, which is the whole economic argument versus an always-on Jenkins EC2 instance
- 04Free tier doesn't expire after 12 months: monthly free build minutes on the smallest EC2 compute types plus free Lambda build seconds
- 05Watch the side costs: S3 artifact storage, CloudWatch Logs, and NAT Gateway charges for VPC-connected builds are billed separately
