Yes the state machine data structure are also used in regex engines. The author of the fst crate also created Rust's regex crate and the ripgrep [0] CLI tool.
The regex crate has multiple implementations of regex matching algorithms, which is exposed as a library [1]. The implementations are selected at runtime based on which is faster and works right for a given regex. See also [2]
No, it isn't. The only similarity between them is finite state machines. Cox's article is about regexes. The fst crate is a data structure for storing keys and optional values. Two completely different things.
