🌲 Responds quickly to webhook events, e.g. from Slack Events API.

Responding quickly helps avoid timeouts and gives the user feedback sooner.

🥦 Checks whether the event has already been received, by looking for a document with the message id in the database.

Webhooks resend events if they fail (e.g. due to timeout). Not doing this check can cause the reply to be repeated.

🌳 If it's a new event, sends a reply.

Replies are defined per webhook, and should consist of a quick initial response to the event, e.g. replying in slack.

🌴 If it's a new event, writes a document to Google Cloud Firestore.

Another function that performs more time-costly work can be set to trigger on new document writes.

🎄 Designed to be deployed as a serverless Google Cloud Function.