If you're not storing anything in it as you said, then the 500MB isn't
for the 'MYSQL' process but it's for the whole XAMPP thing.
Long story short, this is the Mysql configuration file path :
in this file you can find :
key_buffer = 8M
max_connections = 30
query_cache_size = 8M
query_cache_limit = 512K
thread_stack = 128K
This is the MAXIMUM memory the Mysql is using.
Hope this helps.