Manage gym check-ins and subscriptions with Supabase, Google Sheets, and QR codes

Quick overview

Youtube Video: https://youtu.be/QyIalCCy6s8?si=Zlmde_oZz3qbDGwJ
Github Repo: https://github.com/blankarrayy/automated-gym-checkin-system

This workflow handles gym entry via QR codes by validating check-in requests against Supabase subscription data, logging entry attempts in Supabase, it also generates QR codes for check-in and registration and syncs new user IDs to Google Sheets.

How it works

1. Receives a POST request on the /gymcheckin webhook with header authentication and an entry_id query parameter.
2. Looks up the entry_id in the Supabase entry_logs table to detect whether the QR code was already used.
3. If the entry_id is unused, extracts the user ID from the request body and fetches subscription records from the Supabase gym_sub table.
4. Validates that the user exists and has an active subscription, then writes an entry attempt record to the Supabase entry_logs table.
5. Returns a webhook response granting entry (200), rejecting unknown users (401), rejecting inactive subscriptions (401), or rejecting reused QR codes (409).
6. On the /qr-for-gym-checkin webhook, generates a new check-in QR code (pointing to the /gymcheckin URL with a random entry_id) and returns it as a binary image.
7. On the /qr-for-new-account-registration webhook, generates a registration QR code and returns it as a binary image, and on the /account-creation webhook it updates Supabase user subscription data and appends/updates the user ID and name in Google Sheets.

Setup

1. Create Supabase API credentials in n8n and confirm the gym_sub and entry_logs tables (and fields like entry_id, user_id, is_subscribed, and name) match the workflow’s queries and inserts.
2. Add Google Sheets service account credentials, share the target spreadsheet with the service account email, and update the spreadsheet and sheet selection if you don’t use the included IDs.
3. Configure the HTTP Header Auth credential and include the required auth header when calling any of the webhooks.
4. Deploy the workflow and use the production webhook URLs in your QR code scanners and any signup/account-creation source that calls /account-creation.