  Cloud computing is becoming an almost ubiquitous part of the computing
landscape. For many companies today, moving their entire infrastructure and
workloads to the cloud reduces complexity, time to deployment, and saves money.
Spot Instances, a subset of Amazon's cloud computing infrastructure (EC2),
expands on this. They allow a user to bid on spare compute capacity in Amazon's
data centres at heavily discounted prices. If demand was ever to increase such
that the user's maximum bid is exceeded, their instance is terminated.
  In this paper, we conduct one of the first detailed analyses of how location
affects the overall cost of deployment of a spot instance. We analyse pricing
data across all available Amazon Web Services regions for 60 days for a variety
of spot instance types. We relate the data we find to the overall AWS region as
well as to the Availability Zone within that region.
  We conclude that location does play a critical role in spot instance pricing
and also that pricing differs depending on the granularity of that location -
from a more coarse-grained AWS region to a more fine-grained Availability Zone
within a region. We relate the pricing differences we find to the price's
reliability, confirming whether one can be confident in the prices reported and
subsequently, in the ensuing bids one makes.
  We conclude by showing that it is possible to run workloads on Spot Instances
achieving both a very low risk of termination as well as paying very low
amounts per hour.
