Template description
The user has a single arrow, into API Gateway. The gateway then fans out, with one arrow to Auth Service and another to Order Service. Those two calls are drawn as siblings, not as a sequence. Order Service calls Payment Service and Inventory Service. Payment writes Ledger DB. Inventory writes Stock DB. Auth uses User Directory. No arrow runs from the gateway to any database, and the databases do not point back at the services. Auth never calls the order stack. A reader can see three private stores and one front door.
When to use it
Open it when a new engineer assumes the gateway reads the ledger, or when payments and inventory are being drawn as if the gateway called them directly. The sketch is the picture for an ownership talk: each service is the only box touching its store.
How to adapt it
Rename the four services and three stores to the names in your system. If the gateway really does call payments itself, move that arrow off Order Service. Add a return arrow only where a call is synchronous and you need to show the reply. If auth must run before the order call, replace the fan-out with a sequence. Leave User Directory attached to Auth Service unless another service reads it too.