Hi @sam23,
Atlas free tier allow 500 connections and a max of 500 collections (100 databases) in total.
It also allows only 100 crud requests per second at max.
There are more limitations here:
Its hard to.predict how your data will be compressed on disk and it depends on docs structure and data types:
It is possible for mostly text/number documents to be up to 3-5 time compressed.
Please note : we don’t recommend M0 for production usage and it is meant for POC or development only.
Best
Pavel