Inventory Management

When to use

• Designing stock quantity models (available/reserved/committed) and append-only ledger patterns
• Integrating with WMS platforms (ShipHero, NetSuite WMS) or 3PL providers (ShipBob, Flexport)
• Evaluating dropshipping vs. 3PL vs. in-house fulfillment for a new product line
• Building or improving demand forecasting and automated replenishment
• Implementing lot/batch/serial number tracking and expiration management
• Choosing and implementing inventory valuation method (FIFO, LIFO, WAC)
• Setting up multi-location routing, inter-location transfers, or multi-channel inventory sync

Core principles

1. Append-only ledger is the source of truth — never mutate stock counts directly; replay entries for audit
2. Atomic DB operations prevent overselling — UPDATE WHERE available > 0; return row count; skip the SELECT
3. Soft reserve expires, hard reserve holds — cart TTL (15 min) soft; payment confirmed converts to hard
4. Safety stock is not a guess — Z-score × stddev of demand during lead time; recalculate per SKU seasonally
5. One source of truth, push to channels — centralized inventory with per-channel buffer stock; never let channels self-manage

Reference Files

• references/stock-tracking-wms.md — quantity types, ledger pattern, atomic updates, WMS platforms and integration, location modeling, picking strategies
• references/dropshipping-3pl-forecasting.md — dropshipping model and platforms, 3PL providers and integration, in-house vs. 3PL comparison, demand forecasting methods and tools
• references/lot-tracking-valuation-cycle-counting.md — lot/batch/serial tracking, expiration and recall management, FIFO/LIFO/WAC/specific ID valuation, cycle counting process and metrics
• references/multi-location-reservations-sync.md — multi-location routing (DOM), inter-location transfers, backorder/preorder, soft/hard reservation implementation, stock alerts, reorder automation, multi-channel sync