In YAML, this is 9 objects in memory, one of them is a scalar, the other 8 are arrays of size 10 that happen to be pointers to the other objects. Not very big

In YAML, this is 9 objects in memory, one of them is a scalar, the other 8 are arrays of size 10 that happen to be pointers to the other objects. Not very big at all... much less than 1k. It's not even interesting since YAML competently serializes graphs that are far more complex. Lots of reasons to trash YAML, this isn't one of them. As aardvark179 noted, a usage concern with YAML is more with how an unguarded application might fail to check for serialized graph cycles.