question

You're right to be concerned, as that's not going to work. Not the user count - we already support far higher DAU levels, and we've tested to a million concurrent players (which would work out to something like 10-20 million DAU, depending on how you calculate it). The issue is that there are two primary types of general-purpose data in a backend service for online games:

1. Data which is stored across multiple database shards, allowing it to be accessed by all players. This spreads the load for concurrent requests out, and scales to millions of concurrent users. However, it is not something you'd write to from those millions of users - you update it as the owner of the title (so, Title Data and Publisher Data).

2. Data which is custom to the user, and which is only stored in one place. Since it's not sharded, you can't reliably scale this to be used by those millions of users, though a reasonable subset works fine. It's designed to be updated by users, but simply put, the reality of physics makes it so that this cannot be all users, since that would cause a "logjam" effect as you scale up.

Shared Group Data is type 2 - it's designed for a group of players to share and update, though potential collisions do have to be managed carefully. Given the default limits on usage for it in our free service, I wouldn't want to manage more than 100 players in one (and if you wanted to work out a contract with us which provides for a higher limit, I would still not want to go more than a few multiples higher).

What you need is something purpose-designed to the use case, or at least to a use case which is close to your actual design goals, so knowing more about that would be key. It sounds like what you want is a User Generated Content system. If that's what you're going for, we do not have a complete UGC service right now, though if we get enough feedback from developers who need that feature, that could get prioritized into our future updates. If you wanted to build a UGC service on top of our Content service right now, you would need to have custom servers - which you could use our hosting for, potentially - that take care of the key elements - managing reviews and ratings, featuring content from users, and providing the tools needed for your take-down processes. For the database of reviews, you could potentially use the MongoDB add-on we'll be providing soon. That would allow you to design a custom database interaction, while still sending events to your PlayStream to track on everything the players do.