Queue triggered function and load

Question

What happens when several hundred messages are written to a queue and a queue-triggered function begins processing? Does one invocation of the function happen at a time or does another call to the same function begin before the first one is finished?

Answer 1

@bitshift The Function App scales out according to the load. By default, a single instance fetches a batch of messages to process and when scaled out to multiple instances, each instance fetches a batch to process concurrently.

You can read more about queue trigger concurrency in the official reference docs.