[earth2jason]

Well, I think good indexing is key. How do you have your indexes. If they are aligned with what is frequently queried then you should be in good shape. A database of 5-10K users isn't difficult these days for any major DBMS. The key lies in the other things attached to the users and items you query. That can run into the millions. Even that is not much, but depending on how many times you query a million row table, it could put a pinch on your optimization.

Good database mechanics is key. That is the most important thing in my opinion. That is really the whole point in rails when you are deciding relationships. The abstraction in Rails when deciding what should be the best model structure is the same thing as deciding what should be the best and most efficient table structure in your database.

The rave about MongoDB is that it (maybe not quote me on this) "cures" the need for the desire multi-dimensional database. However, even with MontoDB's ability to expand due to it's not needing a pre-defined structure and the ability to expand out dimensionally to a certain extent, PostgreSQL (claims anyways) is still more efficient if you correctly index your tables (think about how you will be querying) and create the correct relationships. Build out models. Allow flexibility.

Also, don't forget caching. Redis and performing jobs is key in certain situations. However, don't get caught up in too much hype. Especially those coming from closed source technologies (Not just talking about caching technologies here but everything in general). They will sell and produce an atmosphere of necessity, but do some research first. Don't follow the heard. I am not going to call anyone out on this. Just do the research and think why is that necessary. I've mentioned Redis a few times and maybe that isn't even necessary either.

Most importantly, put your stuff out there. If it crashes, so what! At least you know you have something. And then you will have people who will give you advice in a coherent direction if necessary.

I salute you in your efforts. Now the most important part is put it out there and kick ass!

You may even want to look into Redis which is a cache system.

[earth2jason]

Also, I forgot to mention since I am miles deep in my own program and hoping a couple bottles of wine will assist me in getting this app hammered out, but make sure you have a good git system going. A live repo, a dev repo and a staging repo at minimum. And at "another minimum", you probably at least want these three repos both on your remote server and local server.

Eventually you will want to maybe bring on other developers. Have a good private repo on Github. That is a choice of course. This way you can choose what to merge into your live branches. You just need to find a good groove. Git is beautiful. It really does help in organization of your development process.

And analytics. I'm a bit absent on this. The reason why is that you are a developer. You will eventually know what you want to know and even if you need to bring on another developer due to time constraints and such, you will know how to develop out personalized analytics that you want out of your app. I mean it is almost evolution. You build an app. Then you want to know what's up. You know the app the best so you will develop loggin and analytical methods to provide you with what you want to know. So again. Unless you are looking at a gem that will help you with visualizing what you are going to develop on the analytical side of things, don't get overwhelmed. You know best. You built it. It's beautiful, and if your app is really a hit, you will plug in chug and make it work.