Business that have purchased more Amazon Web Services (AWS) than they need are about to have an option other than waiting for their subscription to expire. Amazon is working on a new marketplace that will allow customers to buy and sell cloud resources. The cloud exchange is currently under development, and will be used to trade reserved instances, which are cheaper than  on-demand instances, but require a one or three-year commitment.

The marketplace will provide its locked-in customers a little wiggling room. Amazon will charge a 12 percent service fee on transactions in the marketplace. According to the AWS blog:

“If you have excess capacity, you can list it on the marketplace and sell it to someone who needs additional capacity. If you need additional capacity, you can compare the upfront prices and durations of Reserved Instances on the marketplace to the upfront prices of one and three year Reserved Instances available directly from AWS. The Reserved Instances in the Marketplace are functionally identical to other Reserved Instances and have the then-current hourly rates, they will just have less than a full term and a different upfront price.”

The marketplace is just the latest move by Amazon to attract and retain enterprise customers by helping them spend more efficiently. Last month, the cloud giant introduced a tagging system that makes it possible label resources and track who’s using what, and how much.  Amazon currently leads the public cloud space, but new vendors like ProfitBricks with its per minute pricing model, are constantly entering the market attempting to take the leader title from AWS.