Architecture: Nested Groups And Junction

architecture-beta
  group cloud(cloud)[Cloud]
  group api(server)[API Tier] in cloud
  group data(database)[Data Tier] in cloud
  service gw(internet)[Gateway] in api
  service app(server)[App] in api
  service db(database)[Primary DB] in data
  service replica(disk)[Replica] in data
  junction fan in cloud
  service client(internet)[Client]
  client:R --> L:gw
  gw:R -- L:app
  app:R -- L:fan
  fan:R --> L:db
  fan:B --> T:replica