The Lenovo Flex has an HDD storage medium which is better than the SSD storage medium found on most 2 in 1 laptops that have been available for a similar time to it. HDD is a traditional storage drive which stores the information on magnetic disks. HDD drives are slower than other forms of storage such as solid state drives (SSD) and flash drives.
An HDD storage medium is in fact the worst storage medium amongst all notebook PCs of a comparable age and type to the Flex.
Amongst similar types of laptop the best storage medium is SSD.
If the storage medium of this 2 in 1 laptop is too bad for you then you might want to look at the Lenovo Yoga (SSD), or the HP Pavilion x360 (SSD).