Design Safe Configuration and Deployment for Hundreds of Services
Company: Citadel
Role: Site Reliability Engineer
Category: System Design
Difficulty: medium
Interview Round: Technical Screen
# Design Safe Configuration and Deployment for Hundreds of Services
Replace hand-edited files, environment variables, NFS, and SSH scripts for 200-plus multi-region services with controlled configuration and deployment plus rollback.
### Constraints & Assumptions
- Every change is attributable and reviewable.
- Regional rollout can stop independently.
### Clarifying Questions to Ask
- Are secrets included?
- Which services support dynamic reload?
### What a Strong Answer Covers
- Versioned desired state, validation, approvals, rollout agents, health gates, and rollback.
### Follow-up Questions
- How are emergency changes handled?
- How is drift detected?
Quick Answer: Replace hand-edited files, environment variables, NFS, and SSH scripts for 200-plus multi-region services with controlled configuration and deployment plus rollback. Connect requirements and APIs to data modeling, consistency, scaling, failure recovery, observability, and the important design trade-offs.