In this section, we will discuss approaches for implementing high availability in the application and data tiers in the application architecture.
In the application layer, we can do a cold start from pre-configured images or a warm start from scaled down instances for the web servers and application servers in a secondary region. By leveraging auto-scaling we can quickly ramp up these servers to handle full production loads. In this configuration you would deploy the web servers and application servers across multiple AZs (in the primary region) and the standby servers in a separate, secondary region. The standby servers need not be launched till you actually need them. However, ...
