Keystrokes of GNU Readline will timeout it with the specification of “keyseq-timeout” when waiting for the 2nd character after the 1st one. If the 2nd character comes after 1st ESC without timeout it has a meta-property of meta-key to discriminate modified key with meta-key from multibyte characters that come with 8th bit on.
GNU Readline will wait for the 2nd character with “keyseq-timeout” milli-seconds but wait forever after 3rd characters.