It is used for smartphone application performance classification. Application Performance Class 1 (A1) and Class 2 (A2) defines the minimum average of random read/write IOPS. IOPS specification of A1 is read 1500IOPS /write 500IOPS, and the minimum sustained sequential performance is 10MB/s. IOPS specification of A2 is several times faster than A1. The random read is 4000IOPS, and the random write is 4000IOPS. That means the write performance of A2 is faster than A1 read performance, and the minimum sustained sequential performance is also 10MB/s.
*Source: SD Association