CI/CD — Continuous Integration and Delivery

CI/CD is the practice of automatically building, testing, and deploying code every time a change is committed. Continuous Integration (CI) catches integration errors quickly. Continuous Delivery (CD) ensures the software is always in a deployable state. Continuous Deployment takes CD further by automatically releasing every passing build to production.

Why companies use it

·Catches bugs at the moment they are introduced, when they are cheapest to fix
·Reduces the risk of large, infrequent releases by making deployment a routine, automated event
·Enables faster iteration — teams that deploy daily ship features faster than teams that release monthly
·Frees engineers from manual testing and deployment tasks, reducing human error and increasing consistency

What hiring managers look for

·CI/CD is standard practice at modern engineering organisations — engineers without it slow down the team
·Experience setting up or maintaining a CI/CD pipeline (Jenkins, GitHub Actions, GitLab CI, Azure DevOps) is directly practical
·Understanding what tests to run at each stage (unit, integration, smoke, regression) shows maturity
·Engineers who optimise pipeline speed (caching, parallelism) demonstrate systems thinking about developer productivity

Typical interview questions

What is the difference between Continuous Integration, Continuous Delivery, and Continuous Deployment?

What types of tests should be included at each stage of a CI pipeline?

Your CI pipeline takes 45 minutes to run. What strategies would you use to speed it up?

What is a deployment pipeline "gate" and when would you use a manual gate in an otherwise automated pipeline?

Describe a CI/CD pipeline you have built or worked with. What did it build, test, and deploy?

Common mistakes

·Running too few tests in CI — fast pipelines with poor coverage provide false confidence
·Not failing the build on test failures — a CI pipeline that lets failing builds through is worse than no CI at all
·Running all tests sequentially when many can run in parallel — slow pipelines reduce developer feedback loop and get ignored
·Not including static analysis and security scanning in the pipeline — these are cheap to add and catch whole categories of defects
·Treating CD as "deploy everything automatically" without considering blue/green deployment, canary releases, or feature flags for risk management

Real engineering example

An embedded software team's manual test and release cycle took 3 days per release. After implementing CI/CD with GitHub Actions, every PR triggered unit tests (5 min), hardware-in-the-loop integration tests (20 min), and a hardware emulator smoke test (10 min). Failed builds blocked merge. Release was triggered by tagging — the entire build, sign, and deploy to test firmware took 35 minutes. Release cadence improved from monthly to weekly and regression escape rate dropped from 2.3 issues/release to 0.4.

Topics covered

CI/CDcontinuous integrationcontinuous deliveryGitHub ActionsJenkinspipelineDevOps

Related interview guides

Software Engineer →Embedded Software Engineer →Firmware Engineer →Devops Engineer →

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