This val.town project catches webhooks from Notion, makes changes to the data payload, and sends those changes back to Notion as page updates.

Here's one of the examples, which uses val.town to update database pages with favicons from the web:

Read up on it and try the examples: https://www.notion.so/bradnoble/val-town-for-Notion-1cbc200736c2807bb445eccf64d0afe9?pvs=4

This is done in the webhookAPI file.

Every minute, this project has a cron that resets all the state, so that the next visitor to the Notion page has a clean experience. That cron uses the subdomain as the prefix for all the blob storage.