Supabase dev here but not a developer of this particular project, so I don't have the exact details or numbers, but for sure be considerate using a tool like this, it can add loading challenges in a number of dimensions.

In particular when it comes to the database side you're going to want to limit individual realtime event writes. I suggest write to an append only log table and process the data in batches using a background worker.

If you intend to insert every event one by one and index them various ways and have foreign keys to and from, inserting is going to incur a high cost. This can be mitigated for the most part with temporal partitioning, but even then it might be fine for you use case or analytic case to do background updates over an append only log and keep your appends quite fast.

As for the network traffic and loading of the HTTP front end someone else on the team can maybe chime in on that.

EDIT: Note this is very broad advice for any realtime app and not specific to this product.