Google Sheets Two-Way Sync for ERPNext

We build a proper Frappe app — its own module, DocTypes, and hooks.py wiring — installed on your ERPNext site. A Sheet Sync Profile DocType defines each connection: the Google spreadsheet ID and worksheet, the target ERPNext DocType, the field-to-column mapping, the sync mode, and the schedule. Authentication is a Google service account whose JSON key is stored server-side (never in the browser), so the sheet is shared to the service account email and no per-user OAuth dance is required. Column-to-field mapping is configured through a child table in the UI — no code editing to add or remap a field — and each mapping can carry a light transform (date parsing, number coercion, Link-field resolution by name) so a messy spreadsheet lands as clean ERPNext data.

Technically, the engine runs on Frappe's scheduler. You choose hourly, daily, or a specific cron expression, registered under scheduler_events in hooks.py, and the job runs in the background worker — not the web request — so large sheets never time out. Insert mode appends new rows; upsert mode uses a key column you nominate (e.g. an email, an item code, an external ID) to update the matching ERPNext document or create it if absent, via frappe.get_doc / db lookups with permission checks intact. Incremental sync tracks a per-profile watermark (last-synced row or a timestamp column) so each run only processes what changed instead of re-importing the whole sheet. Every run writes a Sheet Sync Log row — counts of inserted, updated, skipped, and errored records, with per-row error detail — so you can see exactly what happened and re-run a failed batch. The optional two-way write-back is driven by ERPNext doc_events (on_update, after_insert) hooks that push the changed document back to the mapped worksheet through the Google Sheets API, with loop-prevention so a sync-in doesn't trigger a sync-out ping-pong. Whitelisted methods expose a manual "Sync now" button and can be called from the Frappe REST API for on-demand runs.

Because this is build-to-order, nothing is a mystery download. We start with a short scoping call to confirm your DocTypes, the worksheets, the key columns for upsert, and whether you need write-back. We build against Frappe/ERPNext v15 or v16, validate on a staging copy of your site with your real sheets during UAT, then install on production with a rollback plan. You receive the full app source in a git repository you own, along with install and configuration docs, a user guide, a training session, and a post-go-live support window. Typical delivery is 2–4 weeks from confirmed scope, depending on how many DocTypes and transforms are in play.