How does Google App Engine manage sessions inside cluster?

Question

A cluster contains several nodes, and if one of current node is down, other nodes can retrieve current user session.

I was thinking about how to do the same thing myself (session replication) if I want to create my own high availaible Paas (Cloud).

May I use a key/value database (NoSQL) in order to store/retrieve sessions ? Or something similar.

How does Google for its Google App Engine ? Does Google use a Filter in order to rewrite HttpSession API (Java) ?

Thanks

Answer 1

in appengine, the session is simply kept in its datastore. you can do the same or improve it by adding a caching layer with memcache.