Configuration Service — Detailed

flowchart TB
  subgraph Admin
    UI([Web UI])
    CLI
    API[REST API]
    GITOPS[Git source of truth]
  end

  subgraph Core
    CFG[Config Service]
    AUTH[AuthN / AuthZ]
    VAL[Schema validation]
    REVIEW[Approval / 4-eyes]
    HIST[(Version history)]
    PROMO[Promotion: dev -> stage -> prod]
  end

  subgraph Store
    KV[(Versioned KV<br/>etcd / Consul / S3)]
    PUBSUB[[Pub/Sub on key changes]]
    LABELS[Targeting: env / region / cohort]
  end

  subgraph Clients[Client tier]
    SDK([Client SDK])
    AGENT[Sidecar agent / Sidekick]
    CACHE[Local cache + TTL fallback]
    WATCH[Watch / long-poll / xDS]
  end

  subgraph Safety
    AUDIT[Audit + diff log]
    ROLL[Rollback / kill switch]
    CANARY[Canary rollout %]
  end

  Admin --> Core --> Store
  Store --> Clients
  Safety --- Core

    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 UI,SDK client;
    class API,GITOPS,CFG,AUTH,VAL,REVIEW,PROMO,LABELS,AGENT,CACHE,WATCH,AUDIT,ROLL,CANARY service;
    class HIST datastore;
    class PUBSUB queue;
    class KV storage;

Glossary & fundamentals

Concepts referenced in this design. Each row links to its canonical page; the tag column shows whether it is a high-level (HLD) or low-level (LLD) concept.

Tag	Concept	What it is	Page
HLD	Pub/Sub & message brokers	topics, consumer groups, delivery semantics	pub-sub-pattern
HLD	Realtime protocols	WS / SSE / polling / gRPC streaming	realtime-protocols
HLD	Service mesh	sidecar mesh, mTLS, traffic policy	service-mesh
LLD	REST API design	verbs, statuses, pagination, errors	rest-api-design