What is a Spoke Gateway?
It is a software appliance that is part of Aviatrix secure cloud networking control and d data plane working as a tunnel between networks.
As of today, Aviatrix software version 6.8 does not support scale groups or scale sets.
HA Options
The Controller monitors the spoke gateways, detects problems, and handles fail-over automatically. There are two options to choose from:

- High Availability Peering: it provides a recovery time of ~30 seconds using a second gateway to form an HA pair.
- Single AZ: The recovery time for this option is approximately 4-5 minutes. As the name suggests, a second gateway is not deployed.
Those times can be tuned and they depend on the CSP as well.
Gateway Keep-alive
The gateway sends periodic keep-alive messages to the Controller:
A gateway is considered in healthy state if controller receives at least 2 messages between two consecutive health checks.

There are three speeds:
- fast: gateway sends keep-alive every 3 seconds and controller checks health every 7 seconds. This option provides a detection time of 14 seconds.
- medium: gateway sends keep-alive every 12 seconds and controller checks health every 60 seconds. This option provides a detection time of 120 seconds.
- slow: gateway sends keep-alive every 60 seconds and controller checks health every 300 seconds. This option provides a detection time of 600 seconds.
Testing
Single AZ

I’m testing the Single AZ shutting down the gateway from the portal:

In this simple test 53 pings were lost.