System Design: Multi‑Tenant CI/CD Platform

Context

Design a cloud-native, multi-tenant CI/CD platform that integrates with popular source control providers. Assume you can use managed cloud services and/or Kubernetes. Support Linux runners by default, with an option to extend to Windows/macOS via dedicated pools.

Requirements

1) Architecture and Key Components

Specify a high-level architecture and the responsibilities/choices for:

• Source control integration (OAuth/apps, webhooks, Git mirroring)
• Pipeline scheduler/executor
• Build runners/agents
• Artifact and image storage
• Secret management
• Caching (source, dependency, build cache)
• Queue/stream for scheduling
• Metadata database
• External and internal APIs (REST/gRPC/webhooks), including eventing

2) Multi-Tenancy and Security

Explain how you ensure:

• Tenant isolation (namespaces, per-tenant runner groups, network and data isolation)
• RBAC with role scopes and secret scoping
• Rate limiting and quotas (API, concurrency, storage)
• Protection from noisy neighbors (fair scheduling, resource limits)

3) Pipeline Execution Semantics

Describe:

• DAG model, conditionals, matrices
• Retries/backoff, timeouts, cancellations
• Idempotency and deduplication

4) Scaling

Cover:

• Autoscaling runners/agents
• Horizontal scaling and sharding of the control plane and scheduler
• Multi-region considerations (if any)

5) Cost Tracking and Billing per Tenant

Describe meters, aggregation, and how you attribute cost by tenant/project.

6) Observability and Compliance

Include:

• Logs, metrics, traces, correlation IDs
• Audit logging and retention
• Disaster recovery strategy
• Zero-downtime deployments and backward-compatible migrations

7) Trade-offs

Compare:

• Shared vs dedicated runner pools
• Managed vs self-hosted agents

8) Deployment Plan

Outline how you would roll out the system in phases, including validation and guardrails.