Speeding up CI/CD pipelines while keeping them reliable and trustworthy.
Speeding up CI/CD pipelines while keeping them reliable and trustworthy.
Lesson outline
Many teams start with a single, long pipeline job: build, test, and package all in one step that can take 30–60 minutes. When it fails, you learn about it late.
Optimization is about turning that monolith into smaller, parallelized stages with caching so you get useful feedback in minutes instead of an hour.
Before vs after pipeline optimization
Before: single long job
After: cached + parallelized jobs (faster feedback)
Cache dependencies and build artifacts between runs (for example, language package caches, Docker layers, or compiled assets). This avoids re‑doing the same heavy work every time.
Split independent tests into parallel jobs so total time drops without losing coverage. For example, run unit tests, integration tests, and UI tests in separate jobs that can run at the same time.
Flaky tests erode trust in CI. When a pipeline is “red” half the time for no good reason, engineers start ignoring it.
Track flaky tests explicitly, quarantine them if necessary, and invest time in fixing root causes (test data, timeouts, ordering issues) instead of adding infinite retries.
Measure your current pipeline: total runtime, longest stage, and most frequent failure points. Treat these like bottlenecks in a value stream.
Add one cache (for example, dependencies) and one parallel job. Re‑measure and compare before/after. Iterate until the majority of commits get usable feedback in under 10 minutes.
DevOps and SRE interviews: expect questions about measuring and improving pipeline performance, dealing with flakiness, and understanding the developer behaviour consequences of slow pipelines.
Common questions:
Strong answer: Framing pipeline speed as a developer productivity and deployment safety issue. Knowing specific caching strategies (layer caching, dependency caching, compiled asset caching). Understanding that flaky tests require root cause investigation, not just retries.
Red flags: Treating pipeline speed as unimportant ("developers can wait"). Suggesting retries as the solution to flaky tests. Not knowing what caching strategies are available in the CI tool.
Quick check · Pipeline optimization
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💡 Analogy
A CI pipeline is a factory production line, and pipeline optimisation is lean manufacturing applied to code delivery. The key lean concept is "eliminate waste": every minute a build spends waiting for a sequential dependency that could run in parallel is waste (waiting waste). Every minute spent re-downloading the same npm packages is waste (rework waste). Every re-run caused by a flaky test is waste (defect waste). The goal of pipeline optimisation is not to make each step faster in isolation — it is to reduce total cycle time from commit to deployable artifact by identifying and eliminating waste in the flow.
⚡ Core Idea
Pipeline time is a proxy metric for developer feedback loop speed, which is a proxy for deployment frequency, which is a proxy for mean time to recovery. Making pipelines faster is not a quality-of-life improvement — it is a reliability engineering investment.
🎯 Why It Matters
DORA research shows that high-performing engineering teams have deployment frequencies measured in hours or days, not weeks. Fast pipelines are a prerequisite: you cannot deploy frequently if each deploy attempt takes an hour to validate. Pipeline optimisation is the engineering work that unlocks the deployment frequency that enables fast recovery from production incidents.
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