Is Lua still used in Casbin and are policy rules stored in memory?

I took a look at Casbin's PERM policy modeling language paper https://arxiv.org/abs/1903.09756; and got as Lua is used;

1. Is it before or still used? If so, in which part of the project does Lua used?

2. Are policy rules still stored in the memory? If so even it remove loading overhead; what if the policy rules are growing?

the current casbin uses expr libs, for lua, go to https://github.com/casbin/lua-casbin

see https://casbin.org/docs/performance