Design a Multi-Tenant CI/CD System Triggered by Git Pushes

Context and Assumptions

• An internal service sends a push event for each Git push containing: tenant ID, repository ID, and repository state (e.g., commit SHA, branch).
• Each repository defines a workflow in a single YAML file at a fixed path (for example, .ci/workflow.yaml).
• A workflow is a sequence (or DAG) of jobs; each job has steps/commands and may depend on others.
• Users must be able to see live job logs and execution status while runs are in progress.

Requirements

Describe the overall architecture and these components:

1. Event intake and trigger handling.
2. Workflow YAML retrieval, parsing, and execution planning.
3. Orchestration and job scheduling.
4. Execution/runners and isolation model.
5. Live log and status streaming to users.
6. Storage of run metadata, logs, and artifacts.
7. Cross-cutting: tenant isolation, fairness, and fault tolerance.

State design choices, key data flows, and how the system scales.