Values:
INSTANCE_SIZE_UNSPECIFIED (0):
Unspecified instance size
EXTRA_SMALL (1):
Extra small instance size, maps to a scaling
factor of 0.1.
SMALL (2):
Small instance size, maps to a scaling factor
of 0.5.
MEDIUM (3):
Medium instance size, maps to a scaling
factor of 1.0.
LARGE (4):
Large instance size, maps to a scaling factor
of 3.0.
EXTRA_LARGE (5):
Extra large instance size, maps to a scaling
factor of 6.0.