When do I need to use 64-bit Azure Functions?

Question

I stumbled upon this answer from 2016 (with an update in 2017) where 64-bit functions were in a very nascent, untested state.

As 32-bit is still the default for new Azure Functions, and that the memory footprint of an 64-bit application is higher than a 32-bit one, what should you consider in your decision to toggle the 64-bit mode in Azure Functions?

Answer 1

As far as I know, we don't have to think about it too much when toggle the 64-bit mode as 32-bit packages are compatible on 64-bit(if toggle from 64-bit to 32-bit, maybe we need to think about it). One thing we need to know is if use app service plan for the function, we need to choose the service plan which the tier higher than "basic".

Answer 2

Consider using 64-bit if your memory usage has the potential of being higher than 2 GB. 32-bit processes can't allocate more than 2 GB of memory (source). 64-bit processes will be able to use all the memory allocated to the VM.

The other case would be if you have any native dependencies that require running in 64-bit mode.