So I'm not an expert in Google's front-ends and I'm not sure that Google stores "sessions" in the way you'd generally think of them in web apps. But usually wh

So I'm not an expert in Google's front-ends and I'm not sure that Google stores "sessions" in the way you'd generally think of them in web apps. But usually when we have requirements like what you'd need for sessions (highly available, low-latency, highly scalable) we use Megastore: http://www.cidrdb.org/cidr2011/Papers/CIDR11_Paper32.pdf http://www.cidrdb.org/cidr2011/Papers/CIDR11_Paper32.pdf http://www.readwriteweb.com/cloud/2011/02/megastore-googles-answer-to-no.php http://www.readwriteweb.com/cloud/2011/02/megastore-googles-... Megastore is a layer on top of Bigtable that adds indexing, synchronous replication across data centers, and ACID semantics within small partitions called "entity groups."