Scaling out to Azure using Azure Container Agent, the Azure Container Instances (ACI) is ideal for transient workload like spinning up a container agent to run your build, test, and push the build artifacts to say Azure storage. You have an economical way to scale out without the burden of provisioning and managing the infrastructure.
ACI also provides per second billing based on the capacity you need. Since spinning up an ACI agent is easy and fast, when your build is complete, just tear the agent down. You do not need to pay for any idle time.
Read about it in the Azure blog.