The term you want is “microSD express”. That is the standard for PCIe and NVME on microSD cards. It specs out at about 1GB/second transfer rates.
Fun engineering decisions: It can use RAM from the hosting computer to store its logical block mapping tables so it doesn’t have to have DRAM onboard for that. That’s a clever way to use what the host has in abundance to avoid putting it on the price and volume constrained microSD card.
Now… how you are going to get the heat out of it when it is running at 1GB/sec. I wonder if we will see new microSD sockets with integrated heat sinks.
Solder the microSD and use the solder-points for thermal connection to the board, like for most other medium-power ICs. It is also cheaper than a socket.
Unfortunately I have not found microSDs suitable for reflow soldering. Typically one uses eMMCs instead, which are very similar, but has a much higher price (and reliability).
I'm surprised that eMMC hasn't seen more of a price drop off like SSDs, mSD and other flash storage. The OrangePi PC+ does include 8GB of eMMC, but I think that was the largest they could get for a cheap price...
Fun engineering decisions: It can use RAM from the hosting computer to store its logical block mapping tables so it doesn’t have to have DRAM onboard for that. That’s a clever way to use what the host has in abundance to avoid putting it on the price and volume constrained microSD card.
Now… how you are going to get the heat out of it when it is running at 1GB/sec. I wonder if we will see new microSD sockets with integrated heat sinks.