mermaid でシステム構成図を描いてみる。
```mermaid flowchart LR subgraph C1[Device] end subgraph C2[LB] NW{{lb1}} end subgraph C3[Backend API1] end subgraph C4[Backend API2] end subgraph DB[db] ST{{DB}} end C1 --> C2 C2 --> C3 C2 --> C4 C3 --> DB C4 --> DB ```