Design a Distributed Config Management Service

Requirements

• •Allow storing, updating, and deleting configuration keys with namespace isolation
• •Provide a Watch API so clients are notified within 1 second of any config change
• •Maintain a version history for every key with the ability to roll back to any previous version
• •Support atomic compare-and-swap (CAS) operations for conditional updates
• •Enforce namespace-level ACLs: services can only read/write their own namespace

Non-Functional Requirements

• •Write latency < 10ms (p99) for a 3-node cluster
• •Watch notification delivery < 1 second
• •Support 10,000 concurrent watch subscriptions
• •System maintains availability with 1 node failed in a 3-node cluster

Constraints

• •Configs are small key-value pairs (< 1MB per value)
• •Strong consistency is required: a config change visible to one client must be visible to all
• •The service must remain available during a minority of node failures (quorum-based)

Evaluation Criteria