A zero-footprint cloud
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Let us consider a cloud infrastructure shared by 1000 clients. Each instance in the cloud is dedicated to a given client. Let us assume a single instance can handle 10 concurrent requests. Also, the time window for processing a request is 5s, reflecting the required timeliness of a financial transaction or the shrinking attention span of a modern web user.

Traditional   Erlang on Xen
Startup time of a new instance is 20s Startup time of a new instance is 100ms
If more than 10 concurrent requests are received for a single client, only 10 of them get handled Instances are provisioned after the request arrival - all requests get handled
At least 1000 instances must be always running (1 per client) and many requests are still left unhandled No instances are running waiting for requests - the cloud footprint is zero
The size of infrastructure is dictated by the number of clients - at least 128 servers are needed The size of infrastructure is proportional to the maximum load - 8 servers may be enough