Hi guys, I'm doing a web app that will be available in various countries and I need it to be quick enough. That's why I'm wondering if keeping a separate database for each country would be faster than using a common database and filtering the results by country?

Well, do some testing.
Apart from that it all depends of the data structure and your indexes. And your programming skills.
With a bunch of properly designed tables and indexes I doubt that with a standard web application with at most a few 10.000 entries per table you will see any performance loss with the single table approach. The multiple table approach means also that you would be duplicating data structures which is always bad.

I'll do some tests as you said. But I'll like to hear some opinions since I'm not specially skilled in database design... and no, this is not a regular app since it will store more than 200.000 entries per country and thats scares me a lot :S


It should not scare you. You need properly designed indexes so that your query can make use of them. Test your main queries against the database design with the "EXPLAIN <query>" statement which will tell you if your indexes are really made use of in the query.