Design a CI/CD pipeline
Overview
This question evaluates a candidate's competency in designing scalable, secure, and cost-effective CI/CD platforms for polyglot microservices, encompassing architecture, build isolation and caching, dependency management, testing orchestration, artifact versioning, deployment strategies, observability, secrets management, governance, and supply chain security. Commonly asked in system design interviews to assess architectural trade-offs and operational reasoning for cloud-native delivery pipelines, it falls under the System Design domain and tests both high-level conceptual understanding and practical application of deployment automation, scalability, reliability, and compliance controls.
System Design: Scalable CI/CD for Dozens of Microservices
Context
You are designing a CI/CD platform to support dozens of polyglot microservices (e.g., Go/Java/Node/Python) deployed to Kubernetes on a major cloud provider. The organization needs fast, reliable, compliant delivery with robust security and observability.
Task
Design the end-to-end CI/CD architecture and explain how it scales and remains secure and cost-effective. Cover the following:
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Triggers and Workflow
- Supported triggers: push, pull request, schedule, manual.
- Branching strategy and environments (dev/staging/prod).
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Build and Dependencies
- Build isolation, reproducibility, and caching (container layer cache, remote cache, language caches).
- Dependency management (lockfiles, proxies/mirrors).
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Testing Strategy
- Orchestration for unit, integration, and end-to-end tests.
- Parallelization/sharding, data setup, flaky-test handling.
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Artifacts and Versioning
- What artifacts are produced (images, packages, Helm charts).
- Versioning scheme, metadata, immutability.
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Promotion and Deployment
- Environment promotion model (e.g., GitOps).
- Deployment strategies: rolling, blue/green, canary with automated analysis.
- Rollback strategy.
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Observability
- CI/CD pipeline observability and application runtime observability (logs, metrics, traces, alerting).
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Secrets and Access
- Secret management, short-lived credentials, separation of duties.
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Scaling the Platform
- Runners/executors autoscaling, isolation, caching at scale.
- Supporting monorepo vs. multirepo.
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Governance and Compliance
- Approvals, change management, policy-as-code, auditability.
- Reliability and Recovery
- Rollback and disaster recovery for both apps and the CI/CD platform.
- Cost Controls
- Techniques to control compute, storage, and tooling costs.
- Supply Chain Security
- SBOM, signing, provenance/attestations, admission controls.
- KPIs/SLOs and On-call
- Key delivery and platform KPIs/SLOs.
- On-call playbook for failed deployments.
Provide assumptions if needed and clearly justify design choices.
Solution
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