German sellers on OTTO Market (OTTO.de, the country's #2 marketplace) usually run their catalog and pricing on OTTO's Partner Connect API while running finance, stock and fulfilment in ERPNext. Out of the box, ERPNext has no concept of an OTTO order, an OTTO listing, or an OTTO settlement — so teams end up copy-pasting orders into Sales Orders by hand, exporting stock levels to CSV, and reconciling OTTO payouts against invoices in a spreadsheet. That manual bridge breaks the moment volume grows: oversells because stock lagged, missed shipping SLAs because tracking never got written back, and month-end chaos because nobody can tie OTTO's settlement report to Sales Invoice lines. ERPNext native runs out of road exactly where a marketplace needs it: a live, two-way, API-driven link.

The ERPNext OTTO Market Connector is a proper Frappe app (its own module, installed via bench get-app / bench install-app) that we build and tailor to your OTTO account and your ERPNext configuration. It ships new DocTypes — OTTO Settings (single, holds OAuth client credentials, marketplace/brand IDs, warehouse and price-list mapping), OTTO Order, OTTO Listing, OTTO Settlement and a mapping DocType that links OTTO SKUs to your ERPNext Item codes. A scheduler_events hook (short-interval and daily cron) polls OTTO Partner Connect for new and updated orders and pulls them into ERPNext, creating a Sales Order (and optional Delivery Note / Sales Invoice) with the correct customer, taxes and item lines. hooks.py doc events (on_update, on_submit, on_cancel) on Item, Item Price and Bin push listing data, price changes and available quantity back to OTTO so your shop never advertises stock you don't have.

Technically, the connector is built the way a maintainable Frappe app should be: OTTO API calls run through a typed client with token refresh, retry/backoff and idempotency so a re-poll never duplicates an order; long or bulk operations (initial listing push, settlement import, catalog resync) run as background jobs via frappe.enqueue so they never block the web workers; and every request/response and error is captured in an OTTO Sync Log DocType for auditability. We expose whitelisted methods (@frappe.whitelist()) for manual "resync this order" / "repush this listing" actions and, where you want a live storefront trigger, thin endpoints over the Frappe REST API. Inventory and price sync are genuinely two-way with a configurable source-of-truth so ERPNext and OTTO don't fight each other. Shipping and tracking numbers entered on the ERPNext Delivery Note are written back to OTTO to close the fulfilment loop, and OTTO settlement files are imported and matched against invoices to make reconciliation a report instead of a spreadsheet. Access is governed by a dedicated role and role profile so only authorized users touch marketplace settings, and a few client scripts add the "Sync now" buttons and status indicators your operators actually use. It is built and tested against Frappe/ERPNext v15 and v16.

Because this is build-to-order, you are not downloading a generic plugin and hoping it fits. After a short scoping call we confirm exactly which OTTO flows you need, which warehouses and price lists map where, and how orders should land in your ERPNext workflow. We build your version, test it on a staging copy of your site with your real OTTO sandbox/credentials, run UAT with your team, then install it on production with a rollback plan. Typical delivery is 2-4 weeks from confirmed scope. You receive the full source in a git repository you own, documentation, training, and a post-go-live support window — no lock-in, no black box.