Just to give you some rough range, Redis is in the range of 10k query/second on an entry level laptop. As you can guess the main bottleneck is the networking I/O with things like Memcached or Redis.
About the speed of dumping the DB. 1 million keys DB with 16 bytes string inside every key takes something like 1 second to be saved on the same HW. For the next release I hope to have replication and LZO compression of (compressible) big values working.