AWS with Google Tag Manager and Firestore

While Google Tag Manager server-side on AWS could potentially query Firestore, there are some important considerations: [1]

• GTM server-side containers run inside AWS, so any Firestore access would need to go through Google APIs over the public internet, which may impact performance.
• You'd need to configure a Google Cloud service account in AWS with the proper Firestore permissions and securely pass the credentials to the GTM container.
• GTM JavaScript variables and tags run at a lower privilege level than server code, so some Firestore operations may not be supported.

As an alternative, you could build a Lambda function that queries Firestore and passes the results to the GTM container as custom JavaScript variables. This keeps the Firestore access centralized in AWS rather than distributing credentials. Some key steps:

• Use AWS Secrets Manager to store your access keys
• Write a Lambda function that uses the service account to access Firestore
• Configure a GTM trigger to call the Lambda function on relevant pageviews
• Return Firestore data from Lambda to populate GTM variables

Let me know if any part of the process needs more explanation. The Lambda approach may perform better while still integrating Firestore data into your GTM container.

Source:

[1]: Guidance for Using Google Tag Manager for Server-Side Website Analytics on AWS