Trendyol stock sync: from Excel to real-time in 7 days

Every Trendyol seller we talk to has told us the same story. A sales spike hits. The Excel-to-Trendyol upload hasn't run in 6 hours. By the time someone notices, 40 orders are in for a product with 3 units in stock.

The refund email doesn't just cost the refund amount. It hits your Trendyol seller score, your shipping reliability metric, and — if it happens twice — your ad budget efficiency. The margin hit compounds quickly.

Day 1-2: audit the data sources

Before writing any code, we map where stock lives. For most brands it's 2-3 places:

• ERP (Logo, Mikro, Netsis, Zirve) — source of truth for actual warehouse.
• Own website — often derived from ERP via a nightly cron.
• Trendyol — manually uploaded or synced via vendor tool.

We pick ERP as the single source of truth. Website and Trendyol become derivatives.

Day 3-4: webhook-based order capture

Trendyol's Partner API (v2) supports webhooks for order events. We subscribe to: order.created, order.cancelled, order.returned. Every event hits a queue (usually Postgres or Redis), gets processed with idempotency keys, and flows to the ERP.

Critical: every webhook goes to a retry queue with 3 attempts + dead letter. Trendyol webhooks fail ~0.2% of the time; you cannot treat them as reliable one-shot.

Day 5-6: bi-directional stock push

ERP → Trendyol push runs every 15 minutes (configurable). The payload contains diff-based updates — we only push SKUs that changed since the last sync. This keeps the Trendyol API rate limit happy and gives you a clear audit log per SKU.

For high-velocity SKUs (top 5% of movement), we push on every ERP write event, not on schedule.

Day 7: observability

You cannot trust a sync you can't see. We build a simple dashboard with:

• Last successful sync time per SKU
• Queue depth (pending events to process)
• Failed events with retry status and error message
• Diff view: Trendyol reported stock vs ERP actual stock per SKU

If these four things are green, your inventory is synchronized. If any one drifts, you know before a customer does.

Why not just use Trendyol's vendor tool?

Vendor tools work if your only channel is Trendyol and your catalog is simple. The moment you add Hepsiburada, or a custom price list, or an ERP with non-standard SKU taxonomy, they break. The 7-day investment in a purpose-built sync pays for itself in one season.