Hi. I'm glad you enjoyed it.

Without knowing more about your code or the architecture of your app, you are saying you're using AWS serverless. The AWS lambda runs node which means you can set up an express server which serves an API endpoint you can send payloads from the client to.

This means you can attach the uID from Firebase Auth to your payload object before you send it to the server. (userId, ownerId or something similar).

The express server on your node runtime in AWS lambda will deal with communication with MongoDB.

Though I must say, it's kind of a weird setup you have there, as both Google, AWS and MongoDB provides much of the same functionality, both for authentication and database.

Google has Firebase, which uses Firebase Auth for authentication and Firebase Firestore as a noSQL database. it also uses Firebase Functions which is the same as AWS Lambda.

AWS has Lamda for serverless, Cognito for authentication and I bet you're familiar with their database options.

MongoDB offers a whole suite of functionality with their MongoDB Realm. I've had some difficulties using Realm with React Native, and since Firebase is so easy use I kind of stuck with it instead.

Regards

Stephan B V