How does digg or any other high-traffic website store user sessions? What do they use for storing the user sessions? File system, DB (which one?), memcache or both?
Let's imagine a simple situation. Logged user has set the flag "Remember me" during login. We've set a session cookie with expiration date 1 year. For example, we are keeping session in memcache, but we also should keep record of this session in DB (in my version). Only users with "Remember me" flag are stored in DB. Is it a right way of storing sessions? I mean high traffic websites, of course (with 2 or more application servers, 2 or more databases, memecache servers etc.). In small websites storing session by default way (in file system) is ok.
I've tried to search google, but failed to find any information about it. I've read some solutions from "Advanced PHP programming" book, but main accent was made to customizing session storing handler.
Really hope to hear good ideas or links!
Thank you.
They are most certainly using memcached or equivalents.