App Engine components
First, we need to understand that each project can only host one App Engine application.
The application can have multiple services with multiple versions, as shown in the following diagram:
Figure 5.1 – App Engine components
Which version is served to the end user is based on the network traffic's configuration. We decide on the percentage of traffic that should be directed to a particular version. This means that it is very easy to make new rollouts and possibly even rollbacks.
