CI/CD Pipelines

Continuous Integration (CI) is the practice of merging code to a shared branch frequently, with each change automatically built and tested to catch integration problems early. Continuous Delivery extends this so the software is always in a releasable state — every change that passes the pipeline could be deployed, but the actual production release is a deliberate manual decision. Continuous Deployment goes one step further: every change that passes all stages is automatically released to production with no human gate. The acronym CD covers both delivery and deployment.

An artifact is the immutable, versioned output of the build stage — a container image, a JAR/WAR, a binary, a package. The principle "build once, deploy many" means you produce the artifact a single time and then promote that exact artifact through dev → staging → production. Rebuilding per environment risks subtle differences (different dependency versions, build flags) so that what reaches production is not what you tested. Storing artifacts in a registry with version tags also enables fast, reliable rollback to a known-good build.

A quality gate is an automated pass/fail checkpoint embedded in the pipeline that blocks progression unless defined criteria are met: all tests pass, code coverage stays above a threshold, static analysis/SAST finds no critical issues, no high-severity dependency vulnerabilities, lint and formatting are clean. Gates encode the team's definition of "good enough to proceed" so quality is enforced automatically rather than relying on human discipline. A failing gate stops the build and surfaces exactly what must be fixed, shifting quality checks left to where they are cheapest to address.

In a blue-green deployment, you maintain two production environments. "Blue" serves live traffic while you deploy and smoke-test the new version on the idle "green." When green is verified, you flip the router/load balancer to send all traffic to green instantly. The big advantages: near-zero-downtime cutover and instant rollback (flip back to blue if something is wrong). The cost is running double the infrastructure during the switch. It contrasts with a canary release, which shifts traffic gradually rather than all at once.

A canary release (named after the "canary in a coal mine") exposes a new version to a small slice of traffic — say 1%, then 5%, then 25% — while closely watching error rates, latency, and business metrics. If the canary stays healthy, you progressively increase its share until it serves everyone; if metrics degrade, you halt and roll back, having affected only a small fraction of users. This limits the blast radius of a faulty release and surfaces problems that only appear under real production traffic, which staging cannot fully reproduce.