Sequence Diagramsequenceeventsorders

Event-Driven Order Processing Sequence

Use this Mermaid sequence diagram to document asynchronous order processing with OrderCreated events, message queues, inventory reservation, payment handling, shipping creation, and dead-letter queue recovery.

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Use Cases

Document event-driven order fulfillment across inventory, payment, shipping, and DLQ recovery

Explain why the order API publishes events instead of calling downstream services directly

Review stock reservation, payment failure, out-of-stock, and shipment creation paths

Align platform, commerce, and operations teams on asynchronous recovery behavior

How This Workflow Works

Step	Purpose
Publish order event	The order API emits OrderCreated to decouple order entry from inventory, payment, and shipping services.
Reserve inventory	Inventory consumes the order event, reserves stock when available, and publishes the next event.
Charge payment	Payment consumes the reservation event and either advances fulfillment or triggers stock release.
Create shipment	Shipping consumes the completed payment event and emits ShipmentCreated after fulfillment work begins.
Handle failures	Out-of-stock or unprocessable events are routed to the DLQ for retry, inspection, or manual recovery.

How To Customize

Rename Order API, Message Queue, and domain services to match your production service names

Add retry, timeout, idempotency, or poison-message branches before sending events to the DLQ

Replace OrderCreated, StockReserved, and PaymentCompleted with your actual event names

Add observability messages for tracing, metrics, or alerting at each event boundary

Split the payment and shipping participants when multiple providers or fulfillment partners are involved

Edit This Template Visually

Open this template in the editor to work from the rendered diagram and the Mermaid source together. Click a node in supported flowchart and sequence diagrams to locate the matching code, select source lines to find the related shape, or ask AI to rename, expand, restyle, or rewrite the selected part of the workflow.

Mermaid Source

sequenceDiagram
    autonumber

    box rgba(232, 242, 255, 0.85) Order Entry
        participant OrderAPI as Order API
    end

    box rgba(231, 250, 250, 0.85) Event Backbone
        participant Queue as Message Queue
    end

    box rgba(244, 237, 255, 0.85) Domain Services
        participant Inventory as Inventory Service
        participant Payment as Payment Service
        participant Shipping as Shipping Service
    end

    box rgba(255, 232, 232, 0.85) Failure Channel
        participant DLQ as Dead Letter Queue
    end

    rect rgba(232, 242, 255, 0.55)
        OrderAPI->>Queue: Publish OrderCreated event
    end

    Note over OrderAPI,Queue: Order API publishes an event instead of calling downstream services directly

    rect rgba(233, 249, 239, 0.55)
        Queue->>Inventory: Consume OrderCreated
        Inventory->>Inventory: Reserve stock

        alt Stock available
            Inventory-->>Queue: Publish StockReserved

            Queue->>Payment: Consume StockReserved
            Payment->>Payment: Charge customer

            alt Payment success
                Payment-->>Queue: Publish PaymentCompleted

                Queue->>Shipping: Consume PaymentCompleted
                Shipping->>Shipping: Create shipment
                Shipping-->>Queue: Publish ShipmentCreated

            else Payment failed
                Payment-->>Queue: Publish PaymentFailed

                Queue->>Inventory: Consume PaymentFailed
                Inventory->>Inventory: Release reserved stock
                Inventory-->>Queue: Publish StockReleased
            end

        else Out of stock
            Inventory-->>DLQ: Publish OutOfStock
        end
    end

    Note over Queue,DLQ: Failed or unprocessable events can be sent to the DLQ for retry, inspection, or manual recovery