The pilot light is the next lowest cost DR method after backup and restore. As the name suggests, you need to keep the minimum amount of core services up and running in a different region. You can spin up additional resources quickly in the event of a disaster.
You would probably actively replicate the database tier, then spin up instances from a VM image or build out infrastructure using infrastructure as code such as CloudFormation. Just like the pilot light in your gas heater, a tiny flame that is always on can quickly light up the entire furnace to heat the house.
The following diagram shows a pilot light disaster recovery pattern. In this case, the database is replicated into AWS, with Amazon EC2 instances of the web servers and application servers ready to go, but currently not running:
A pilot light scenario is pretty much similar to back up and restore, where you take the backup of most of the components and store...
