Configuration Service — Simple

Problem statement (interviewer prompt)

Design a configuration service that stores feature toggles + tuning parameters + secrets for 1000s of microservices. Clients read at startup + watch for live updates within seconds. Versioned, audited, RBAC-controlled, and partitioned by environment + region.

flowchart LR
  ADM[Admin]
  CFG[Config Service]
  KV[(Versioned KV)]
  CL([Clients / Sidecars])
  ADM --> CFG --> KV
  CL --> CFG
  CFG -. watch / push .-> CL

    classDef client fill:#dbeafe,stroke:#1e40af,stroke-width:1px,color:#0f172a;
    classDef edge fill:#cffafe,stroke:#0e7490,stroke-width:1px,color:#0f172a;
    classDef service fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
    classDef datastore fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
    classDef cache fill:#fed7aa,stroke:#9a3412,stroke-width:1px,color:#0f172a;
    classDef queue fill:#ede9fe,stroke:#5b21b6,stroke-width:1px,color:#0f172a;
    classDef compute fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
    classDef storage fill:#e5e7eb,stroke:#374151,stroke-width:1px,color:#0f172a;
    classDef external fill:#fce7f3,stroke:#9d174d,stroke-width:1px,color:#0f172a;
    classDef obs fill:#f3e8ff,stroke:#6b21a8,stroke-width:1px,color:#0f172a;
    class CL client;
    class ADM,CFG service;
    class KV datastore;