Fastest recommended MicroSD card?

What is the fastest MicroSD one can get for Nano to get highest IO performance out of it?

I wish it had eMMC slot from the start and not having to wait until June ;)

I’m not sure what is the best, but I’m using a Kingston HyperX 64GB Gaming card. It’s A1 rated, and I picked it because reviews showed that especially random writes usually vastly reduce performance of other cards, but this one hardly budged.

There are others, too, for sure, for example the Sandisk Extreme, Extreme Pro or Extreme Plus, depending on your budget. I’d just check what is available for a good price that has at least U3/V30/A1 or A2 rating in your region and then check its benchmarks, such as here: https://www.cameramemoryspeed.com/reviews/sd-cards/ There you can also sort e.g. via random write speeds, which many cards have problems with.