Rust

These busy loops burn CPU cycles without doing anything. It is almost always a better idea to panic! than to have a busy loop.

.bytes().count() is better written as .len() which is easier to read and more performant.

.bytes().nth(..) is better written as .as_bytes().get(..) which is more performant.

Arc<RwLock<HashMap<K, V>>> has performance concerns, the dashmap crate provides a much better alternative to concurrent hashmaps. Hence, Arc<RwLock<HashMap<K, V>>> is better off replaced by Arc<DashMap<K, V>> from the dashmap crate.

.split_whitespace() produces an iterator with preceding and trailing whitespace removed. Thus, s.trim().split_whitespace() is equivalent to just s.split_whitespace().