Design Delivery Scheduling - System Design | WinJob

Problem Statement: Scheduled Last-Mile Delivery

Problem Statement: Scheduled Last-Mile Delivery for a carrier-scale delivery scheduling platform: shippers book deliveries with time windows and priority tiers; sort hubs batch stops into route plans; drivers execute sequences while the control plane continuously re-validates TW feasibility.

Mechanism (1)

Shipment Plan Command is the sole writer; route geometry and ETAs are derived projections keyed by plan_id.

Operational signals

Watch tw_violation_rate, solver_p95_sec, replan_churn_per_hour, hub_queue_depth, and pod_upload_fail_rate. Page when tw_violation_rate > 2% for 15 minutes in any hub.

Amazon/FedEx/UPS interviews probe time-window feasibility and priority preemption under hub saturation—not generic CRUD.

Design anchors

plan_id: immutable scheduling artifact after booking.
service_date + hub_id: natural partition for solver batches.
priority tier: express > standard > economy preemption rules.
TW slack: operational buffer inside customer-facing window 12:00-17:00.

javaOne Dark Pro

1 public final class PlanCommand1 {
2   private final UUID planId;
3   private final long expectedVersion;
4   private final String hubId;
5   private final Instant serviceDate;
6   public UUID planId() { return planId; }
7 }

pythonOne Dark Pro

1 @dataclass(frozen=True)
2 class PlanCommand1:
3     plan_id: str
4     expected_version: int
5     hub_id: str
6     service_date: date

typescriptOne Dark Pro

1 interface PlanCommand1 {
2   planId: string;
3   expectedVersion: number;
4   hubId: string;
5   serviceDate: string;
6 }

Why interviewers care

Delivery Scheduling interviews reward crisp scope, explicit trade-offs, and failure stories—not generic microservice diagrams.

Interview checkpoint

Name one failure story for Problem Statement: Scheduled Last-Mile Delivery that proves you understand real outages, not happy-path diagrams.

Key Highlights

•Anchor 1-A: plan command owns writes
•Anchor 1-B: hub-sharded VRP
•Anchor 1-C: time-window hard constraints
•Anchor 1-D: priority tier ladder

1	public final class PlanCommand1 {
2	private final UUID planId;
3	private final long expectedVersion;
4	private final String hubId;
5	private final Instant serviceDate;
6	public UUID planId() { return planId; }
7	}

1	@dataclass(frozen=True)
2	class PlanCommand1:
3	plan_id: str
4	expected_version: int
5	hub_id: str
6	service_date: date

1	interface PlanCommand1 {
2	planId: string;
3	expectedVersion: number;
4	hubId: string;
5	serviceDate: string;
6	}