The trick with speeding up rubocop (and most other linters, for that matter) is to run it as a daemon. There's a rubocop daemon gem available. Or with solargrap

The trick with speeding up rubocop (and most other linters, for that matter) is to run it as a daemon. There's a rubocop daemon gem available. Or with solargraph, rubocop is kept in memory so you only pay the startup cost once. With that setup you can get a lint/fix on save in sub 300ms.