Singles Path Service - Domain-Driven Design

Overview

The Singles Path Service manages direct pick-to-pack workflows for single-item orders. It handles approximately 40-50% of all warehouse orders through the most streamlined fulfillment path.

Service Information

Domain Model

Aggregates

SinglesSession (Root Aggregate)

Represents a single-item order session through direct pick-to-pack workflow.

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public class SinglesSession {
    private String sessionId;
    private String orderId;
    private String shipmentId;
    private String workerId;
    private String stationId;
    private SessionStatus status;
    private String itemSku;
    private String assignedPickLocation;
    private String assignedPackStation;
    private LocalDateTime startedAt;
    private LocalDateTime completedAt;
}

State Machine:

stateDiagram-v2
    [*] --> INITIATED
    INITIATED --> PICKING: assignWorker()
    PICKING --> PACKING: completePick()
    PACKING --> COMPLETED: completePack()

    INITIATED --> FAILED: fail()
    PICKING --> FAILED: fail()
    PACKING --> FAILED: fail()

Business Rules:

• Session starts in INITIATED status
• Worker assignment transitions to PICKING
• Pick completion transitions to PACKING
• Pack completion marks session as COMPLETED

Value Objects

PickLocation

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public record PickLocation(
    String locationId,
    String aisle,
    String bay,
    String level,
    String position
) {}

PackStation

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public record PackStation(
    String stationId,
    String zone,
    boolean isExpress
) {}

Domain Events

Events Published

Events Consumed

Domain Services

SinglesSessionService

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public interface SinglesSessionService {
    SinglesSession createSession(String orderId, String shipmentId, String itemSku);
    SinglesSession assignWorker(String sessionId, String workerId, String stationId);
    SinglesSession completePick(String sessionId, String pickLocation);
    SinglesSession completePack(String sessionId, String packStation);
    SinglesSession getSession(String sessionId);
    List<SinglesSession> getSessionsByStatus(SessionStatus status);
}

API Endpoints

Singles Sessions

Workflow

sequenceDiagram
    participant ROUTING as Routing Service
    participant SINGLES as Singles Service
    participant PICKER as Picker
    participant PACKER as Packer
    participant SLAM as SLAM Service

    ROUTING->>SINGLES: ShipmentRoutedToPathEvent
    SINGLES->>SINGLES: Create session
    SINGLES-->>SINGLES: SinglesSessionStartedEvent

    SINGLES->>PICKER: Assign pick task
    PICKER->>PICKER: Pick item
    PICKER->>SINGLES: Complete pick
    SINGLES-->>SINGLES: SinglesPickCompletedEvent

    SINGLES->>PACKER: Direct to pack station
    PACKER->>PACKER: Pack item
    PACKER->>SINGLES: Complete pack
    SINGLES-->>SLAM: SinglesPackCompletedEvent

Repository Interfaces

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public interface SinglesSessionRepository {
    SinglesSession save(SinglesSession session);
    Optional<SinglesSession> findById(String sessionId);
    List<SinglesSession> findByStatus(SessionStatus status);
    List<SinglesSession> findByWorkerId(String workerId);
}

Integration Patterns

Customer-Supplier

• Upstream: Process Path Routing Service supplies path assignments
• Downstream: SLAM Operations Service consumes pack completion events

Conformist

• Pack & Ship: Consumes packing completion events for workflow tracking

Characteristics

Technology Stack

References

• Process Path Overview
• Business Capabilities
• Integration Documentation