Wms Developer

WMS Developer

When to Use

• Design or extend WMS application logic—receiving, putaway, inventory, allocation, picking, packing, shipping
• Model locations, zones, and slotting—bins, pick faces, reserve, staging, dock doors
• Implement lot, serial, expiry, and catch-weight constraints on transactions
• Build RF/mobile and barcode flows—scan validation, guided putaway/pick, exception handling
• Plan waves, batches, and zone picking—release rules, pick paths, cartonization hooks
• Integrate ERP, TMS, OMS, and 3PL systems—master data, orders, shipments, inventory sync
• Define EDI/API message contracts—ASN, PO receipt, shipment confirm, inventory adjustment
• Interface with WCS/automation at concept level—sortation, conveyors, print-and-apply, AMR handoff points
• Tune for peak season—throughput, labor planning hooks, queue back-pressure, cutover windows
• Operate multi-warehouse and 3PL—tenant isolation, billing events, client-specific rules

When NOT to Use

• Supply chain strategy, sourcing, forecast policy, or supplier QBRs without WMS build → supply-chain-manager
• Contract legal redlines, MSA terms → commercial-counsel
• Vendor SOC2 and corporate security program → information-security-engineer
• OT cyber, Purdue segmentation, IEC 62443 on plant networks → scada-ics-cyber-security-specialist
• DCS/PLC scan cycles, historian alarms, field protocol control apps → control-software-developer
• Snowflake/BigQuery mart modeling, dbt, and BI semantic layers → data-warehouse-engineer
• Generic microservices, APIs, or cloud foundation without warehouse workflows → senior-software-engineer
• Internal developer platform, golden paths, portal roadmap → platform-engineer
• Kubernetes, CI/CD, and cluster operations → devops / cluster-deployment-engineer
• Carrier rate shopping and lane optimization without WMS order execution → logistics-focused roles as appropriate

Related skills

Core Workflows

1. Scope and boundaries

Define WMS footprint, tenants, automation touchpoints, and handoffs.

See `references/wms_developer_scope.md`.

2. Inventory and locations

SKU attributes, UOM, location hierarchy, allocation rules, and holds.

See `references/inventory_and_location_modeling.md`.

3. Inbound and outbound

Receiving, putaway, order release, shipping, and exceptions.

See `references/inbound_outbound_workflows.md`.

4. Picking and fulfillment

Waves, batches, pick methods, packing, and cartonization.

See `references/picking_waves_and_fulfillment.md`.

5. Integrations

ERP, TMS, OMS, EDI, APIs, and event patterns.

See `references/integrations_erp_tms_edi.md`.

6. Customization, testing, and operations

Extensions, UAT, cutover, monitoring, and peak readiness.

See `references/customization_testing_and_ops.md`.

Outputs

• Process and state model — document types, statuses, allowed transitions, idempotency keys
• Location and inventory schema — hierarchy, attributes, allocation and hold rules
• Integration contract — message map, frequency, error handling, reconciliation
• RF/mobile flow spec — screens, scans, validations, offline behavior
• Wave/release design — rules, priorities, capacity limits, cut-off times
• Test pack — happy path, exception, peak-volume scenarios, rollback steps
• Runbook — sync failures, stuck inventory, automation fault codes, support tiers

Principles

• Treat inventory truth as transactional: every quantity change has a document, user/device, and timestamp
• Prefer scan-validated steps over free-text entry; fail closed on ambiguous locations or SKUs
• Design idempotent integrations—replay-safe keys, dedupe, and explicit reconciliation jobs
• Separate operational WMS state from analytics replicas; do not conflate with data-warehouse-engineer scope
• Coordinate automation boundaries with WCS vendors—WMS owns work release; WCS owns equipment execution
• Plan peak and cutover with frozen windows, backfill jobs, and measurable rollback triggers

Customization, testing, and operations

Table of contents

1. Customization layers 2. Extension guidelines 3. Testing strategy 4. Cutover and peak readiness 5. Monitoring and support 6. Multi-warehouse and 3PL

Customization layers

Avoid core table hacks; use supported extension points and feature flags per site/client.

Extension guidelines

• Keep business logic deterministic and side-effect free in allocation hooks where possible
• Never bypass scan validation in RF shortcuts
• Log rule version applied to each decision for debug
• Package custom code in CI with same rigor as senior-software-engineer practices
• Document upgrade impact for each vendor release

Testing strategy

Scenario pack (minimum):

• Full inbound ASN → putaway → available
• Multi-line B2C order → batch pick → pack → ship
• Short pick, substitute, cancel mid-wave
• Cycle count adjustment with approval
• Integration duplicate message handling

Cutover and peak readiness

Cutover:

• Freeze master data changes; snapshot balances
• Run parallel reconciliation first day
• Define rollback—revert DNS/integration, restore DB backup only if approved

Peak season:

• Pre-build wave templates and labor plans
• Scale integration consumers and DB indexes
• Throttle non-critical jobs (reports, archival)
• War-room dashboards: open waves, pick backlog, integration lag

Monitoring and support

Alert on:

• Integration queue depth and age
• Failed ship confirms and stuck allocations
• RF login errors and device version drift
• Automation NACK rate from WCS

Tier-1 runbooks: restart print service, requeue message, reprint label, unlock wave. Tier-2: data fix with approval workflow.

Multi-warehouse and 3PL

• Site ID on every record; no cross-site allocation without transfer document
• Client ID for 3PL; row-level security in UI and APIs
• Billing capture on handled units, storage days, VAS tasks—export to billing system
• SLA timers on receipt-to-putaway and order-to-ship by client contract

Separate operational reporting from data-warehouse-engineer marts—use event export or CDC with documented schema.

Inbound and outbound workflows

Table of contents

1. Inbound overview 2. Receiving and putaway 3. Outbound overview 4. Order release and shipping 5. Returns and VAS 6. Exceptions

Inbound overview

Standard flow:

ASN/PO ──► Check-in ──► Receive ──► QA (optional) ──► Putaway ──► Available inventory

ASN (advance ship notice) pre-populates expected lines; receiving matches PO line, qty, lot.

Receiving and putaway

Putaway strategies:

• Directed—system proposes location by velocity, zone, weight, hazmat
• User override—allowed with reason code and supervisor PIN if configured
• Consolidation—merge partial LPNs when rules permit

Outbound overview

Order download ──► Allocate ──► Release (wave) ──► Pick ──► Pack ──► Ship confirm

Support B2B (pallet/case) and B2C (each pick) on same platform with different document types.

Order release and shipping

• Allocation reserves inventory; failed lines → backorder, substitute, or cancel rules
• Wave release creates pick tasks by priority, carrier cut-off, route, or zone
• Pack verifies contents (scan-to-carton), weight, dims, SSCC labels
• Ship confirm posts to ERP/OMS; generates ASN 856, BOL, tracking

Carrier integration (with TMS):

• Rate shop optional at pack; label print at pack station
• Manifest close triggers billing and tracking email events

Returns and VAS

Returns (RMA):

• Inspect grade A/B/scrap; restock, refurb, or destroy paths
• Quarantine until disposition

Value-added services (VAS):

• Kitting, labeling, gift wrap, embroidery—model as work orders consuming components

Exceptions

Document every exception with user, timestamp, reason code, and link to source order/LPN.

Integrations: ERP, TMS, EDI, and APIs

Table of contents

1. Integration principles 2. ERP patterns 3. OMS and e-commerce 4. TMS and carriers 5. EDI message map 6. API and events 7. Reconciliation

Integration principles

• Assign system of record per entity: items (usually ERP), warehouse inventory (WMS), shipment tracking (TMS/carrier)
• Use idempotency keys on every inbound message (messageId, correlationId)
• Prefer async events for high volume; synchronous APIs for low-latency lookups
• Log payload hash, status, retry count; never silently drop failures
• Schedule reconciliation jobs comparing WMS vs ERP quantities and open orders

ERP patterns

Handle partial receipts, over-receipts, and closed PO line rejects explicitly.

OMS and e-commerce

• Order import on create or release from hold
• Cancel/split propagation before pick starts
• Inventory feed—ATP or available quantity snapshots with latency SLA
• Ship confirm + tracking to OMS for customer notifications

TMS and carriers

• Rate shop optional at pack; store selected service level
• Label generation—ZPL/PDF to print server; capture tracking number
• Manifest close-out; PRO/BOL for LTL
• Tracking events inbound to OMS (delivered, exception)

WMS owns carton content; TMS owns carrier contract unless tightly coupled module.

EDI message map

Common retail/wholesale EDI (illustrative):

Map segments to canonical internal models before WMS tables—avoid EDI-shaped tables in core schema.

API and events

Patterns:

• REST/JSON for real-time order and inventory queries
• Webhooks for ship confirm, receipt complete
• Message bus (Kafka/SQS) for peak absorption with consumer groups per site

Version APIs; support backward-compatible fields; document error codes for ops.

Reconciliation

Daily (or hourly) jobs:

• Compare on-hand by SKU WMS vs ERP within tolerance
• List open orders stuck in allocated/picked
• Flag unposted shipments and orphan LPNs
• Produce operator work queue with drill-down links

Escalate persistent drift to integration owner—not ad-hoc SQL in production without change control.

Inventory and location modeling

Table of contents

1. SKU and unit of measure 2. Location hierarchy 3. Inventory dimensions 4. Allocation and ATP 5. Holds and quarantine 6. Slotting and replenishment 7. Common pitfalls

SKU and unit of measure

• Define base UOM (each) and handling UOM (case, pallet) with conversion factors
• Capture catch weight, variable weight, and nested pack hierarchies where needed
• Track attributes: lot, serial, expiry, country of origin, temperature zone, hazmat class
• Enforce receipt validation—weight/tolerance, shelf-life minimum on inbound

Location hierarchy

Typical levels (adjust to product):

Rules:

• Unique location IDs; avoid reusing IDs across sites without namespace prefix
• Mark locations pickable, replenishable, countable, shipping-staging explicitly
• Support virtual locations for in-transit, VAS, and system buffers

Inventory dimensions

Track quantity by:

• SKU + location + LPN/container (license plate number)
• Status—available, allocated, picked, on-hold, damaged
• Lot/serial/expiry when attribute-controlled

Maintain transaction log (immutable) separate from balance snapshot for audit and replay.

Allocation and ATP

Allocation strategies (examples):

• FIFO/FEFO by expiry
• Strict lot for regulated or customer-specific orders
• Zone-priority—pick face first, then reserve
• Substitution rules with approval and audit

Holds and quarantine

Hold types: QA, damage, recall, customs, client embargo. Holds must:

• Block allocation and pick
• Surface reason codes on RF
• Require role-based release with comment

Slotting and replenishment

• Slotting moves fast movers to pick faces; slow movers to reserve
• Min/max and demand-based replen generate move tasks from reserve to active
• Measure pick density and travel time when changing slotting—coordinate with operations before mass moves

Common pitfalls

• Mixing ERP available with WMS available without sync lag documentation
• Allowing negative available without controlled backorder rules
• Splitting lots across picks without capture at pack confirm
• Oversized LPN nesting causing pick-path dead ends
• Missing UOM conversion on case picks leading to short ships

Picking, waves, and fulfillment

Table of contents

1. Pick methods 2. Wave planning 3. Batch and cluster picking 4. Zone and sortation 5. Packing and cartonization 6. Labor and productivity

Pick methods

Pick path optimization:

• Sequence by location pick path (serpentine aisle order)
• Respect weight/volume limits per container
• Split hazmat and temperature zones

Wave planning

Wave = batch of demand released together for picking.

Release criteria examples:

• Carrier cut-off time
• Priority or service level (same-day vs standard)
• Route/stop for retail distribution
• Single-SKU waves for promotional spikes

Wave lifecycle:

Build pool ──► Allocate ──► Release tasks ──► Pick in progress ──► Complete / close

Controls:

• Max lines / units / orders per wave
• Labor capacity caps by zone
• Frozen wave during count or system maintenance

Batch and cluster picking

• Batch: one picker, one SKU, many orders—sortation required post-pick
• Cluster: multi-order cart; scan tote + SKU to confirm placement
• Validate no SKU commingling without scan at sort station

Zone and sortation

• Pick-and-pass: container moves zone to zone; each zone picks its lines
• Put-wall / sort wall: batch pick to wall slots by order
• WCS divert: WMS sends container ID + destination; WCS confirms divert scan

At concept level: WMS publishes work units; automation confirms completion events—never assume silent success.

Packing and cartonization

• Scan-to-pack—each item scanned into carton; short pack blocks close
• Cartonization rules—choose box size by dims/weight; minimize void fill
• Insert rules—pack slips, marketing, hazmat docs per order profile
• Multi-carton orders—parent shipment ID links cartons

Labor and productivity

Metrics (operational, not HR payroll):

• Lines/units per hour by zone
• Travel time estimates vs actual (if captured)
• Exception rate (shorts, mis-scans)

Use metrics to tune wave size and slotting before peak season.

WMS developer scope

Table of contents

1. Role definition 2. In scope 3. Out of scope 4. System landscape 5. Operating models 6. Deliverable checklist

Role definition

A WMS developer designs and implements software that executes warehouse operations: receiving inventory, storing it, allocating it to demand, picking and packing orders, shipping, and maintaining accuracy through cycle counts and adjustments. The role spans configuration, customization, extension code, integration adapters, and operational runbooks—not executive supply chain strategy or plant-floor control engineering.

In scope

Out of scope

• Supply chain strategy without WMS implementation—sourcing awards, safety stock policy workshops → supply-chain-manager
• ERP functional consulting—GL periods, revenue recognition, HR modules
• Pure TMS routing—carrier selection, rate engine, without WMS shipment execution
• OT/ICS security and DCS logic—PLC programs, Purdue zones → scada-ics-cyber-security-specialist, control-software-developer
• Enterprise data warehouse—dimensional models, dbt marts → data-warehouse-engineer
• Generic cloud/K8s without warehouse workflows → platform-engineer, devops

System landscape

Typical integration map (logical):

OMS / e-commerce ──► WMS ◄──► ERP (items, PO, SO, finance)
                        │
            ┌───────────┼───────────┐
            ▼           ▼           ▼
          TMS        WCS/AMR      Label/print
       (labels,      (sort,        services
        tracking)     convey)      

WMS remains system of record for warehouse inventory state and task execution until ship confirm posts upstream.

Operating models

Deliverable checklist

Before go-live, confirm:

• [ ] Document types and status transitions documented
• [ ] Location hierarchy and slotting rules signed off by operations
• [ ] Allocation and substitution rules tested with peak SKU mix
• [ ] RF flows UAT’d on target devices and Wi-Fi coverage
• [ ] Integration replay and reconciliation jobs defined
• [ ] Cycle count and adjustment audit trail verified
• [ ] Automation fault codes mapped to WMS exception tasks
• [ ] Cutover, rollback, and hypercare runbooks approved