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Why inventory sync makes or breaks your margin

Realtime voorraadsynchronisatie via API op variantniveau voor meerdere verkoopkanalen

Nothing costs as much as “overselling” and mis-selling. Any mismatch between actual inventory levels and what your channels show results in cancellations, support tickets and ranking loss (marketplaces penalize out-of-stock). An API-driven setup with a single inventory source makes all the difference: less manual work, more reliability and room to scale.

Core principles for a robust setup

  1. Variant level, not just SKU – Keep stock by variant (size/color). One variant out-of-stock should not block the rest.

  2. Single Source of Truth (SSOT) – One inventory service that writes/reads; all channels consume it.

  3. Event-driven – Webhooks/queue for inventory changes (orders, returns, deliveries) instead of periodic batches.

  4. Rate-limiting & retries – Marketplaces and shops have limits; build in back-off and “at-least-once” delivery.

  5. Idempotential – Each mutation has a unique key (order_id + line_item_id + attempt) to avoid duplicate updates.

  6. Latency budget – Aim for < 2-5s end-to-end update; anything above that increases oversell risk.

  7. Audit & reconciliation – Daily “diff” between SSOT and channels; automatically fix discrepancies.

Practical architecture

  • Input side:

    • ERP/WMS (inbound, pick/pack, counting) → inventory.update events.

    • Supplier feeds/APIs (purchasing/ETAs) → reservations or “coming soon” inventory.

    • Returns/RMA → release after verification.

  • Processing layer:

    • Normalizer maps external variant keys to your variant_id.

    • Rules (safety buffer, channel-specific caps, pre-allocation for top sellers).

    • Queue (FIFO) + retry DLQ.

  • Output side:

    • Shop platform (Shopify/Woo) via Inventory/Stock APIs.

    • Marketplaces (Bol, Amazon) through partner APIs.

    • Ads/catalogs (GMC/Merchant Center) for visibility.

Rules that work in practice

  • Safety stock per channel: hold 1-3 pieces on fast sellers to accommodate overselling at peaks.

  • Min/max exposure: set upper limit per channel (e.g. max 5 visible on marketplace).

  • ETA logic: show “Within 2-4 days” when inbound is confirmed (with date), but push only live when ready.

  • Bundles/kits: stock of kit = minimum of components (and update both directions).

  • Pre-allocation: top-ranked listings get priority with low inventory.

KPIs to drive weekly

  • Overselling rate (< 0.5%)

  • Update latency p95 (< 5s)

  • Reconciliation drift (< 0.2%)

  • Cancel ratio by OOS (< 1%)

  • Support tickets “not available” (↓ trend)

Governance & management

  • Version control of rules (v1, v2) + rollback.

  • Change budget per day/SKU to control price fluctuations (if pricing is also in the flow).

  • Clear ownership: operations (rules), engineering (stability), commerce (channel priority).

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