Since microSD cards are mostly used for media storage these days, sequential speeds matter more, but random access speed is still important. Apps often save data in small chunks scattered across the storage device, so a microSD card used for operating systems, applications, or game save files needs to be fast at reading and writing small bits of data (often around 4 KB) in random locations. Most Android devices no longer let you run apps from external storage, but if your operating system and programs live on the card (as in a Raspberry Pi) or you’re playing a game downloaded to it (as on a Nintendo Switch), it’s important that your random read and write speeds don’t hold you back. Again, all the cards passed the read tests, but two cards were slower than the others.
