What factors are considered when scaling up or down?

There are many factors that CloudOptimo uses during scaling actions. First, the settings for maximum exposure in one spot market and for all spot markets is analyzed to make sure any proposed actions will not violate those settings. Next factors such as the current diversity over markets, prices in different spot markets, when the next time existing instances will incur a charge, and volatility of prices in certain markets are blended together to choose which instance type and spot market to place new instances in, or remove from for scaling down.