Our uptime averaged well over 99% over the past year. Uptime metrics are available to the public here: https://zephyr-scale.statuspage.io.
We have the ability to both horizontally and vertically scale all of our resources (services, databases, and so on) on an increase in demand.
We have the ability to scale our app to respond to an increase in demand and we continuously monitor the system to address any performance issues that occur.
No, although we closely monitor the performance of our production systems and act to maintain and improve it accordingly.