* Use utf8mb4 character set by default `utf8mb4` character set supports supplementary characters including emoji. `utf8` character set with 3-Byte encoding is not enough to support them. There was a downside of 4-Byte length character set with MySQL 5.5 and 5.6: "ERROR 1071 (42000): Specified key was too long; max key length is 767 bytes" for Rails string data type which is mapped to varchar(255)