Yesterday my azure function were crashed and I found this link about best practise to run a healthy app https://azure.github.io/AppService/2020/05/15/Robust-Apps-for-the-cloud.html#use-multiple-instances.
I have a few doubts regarding some parts of the document
If we increase the number of instance, should we scale down the current app service plan. For example, I am using P2V3, after adding another instance I should scale down my plan to P1V3?
I have 4 function apps, currently they are under the same app service plan. After I changed from single instance to 2 instances, can I assume that 2 function apps will be assigned to 1 instance?
Is there a way to scale out automatically if the current instance is down?
In the link I shared above, it mentioned that 'app code should be able to handle multiple instances without synchronization issues when reading from or writing to data sources'. After scaling out, that could be a situation where 2 same functions are running in the same time?
Thanks in advance!