FYI: Your 1b is not the same as other people's 1b: http://aws.amazon.com/ec2/faqs/#How_can_I_make_sure_that_I_am_in_the_same_Availability_Zone_as_another_develo

FYI: Your 1b is not the same as other people's 1b: http://aws.amazon.com/ec2/faqs/#How_can_I_make_sure_that_I_am_in_the_same_Availability_Zone_as_another_developer http://aws.amazon.com/ec2/faqs/#How_can_I_make_sure_that_I_a... Various software used to hardcode 1a, so 1a received disproportionate load. Now, everyone's a-e is randomized among the "true" a-e, meaning that even if everyone hardcodes 1a, the load will still be evenly distributed.