MariaDB 10.1 not only contains tons of new features, it has also been polished to deliver top performance. The biggest improvement has been achieved for scalability on massively multithreaded hardware.READ MORE
There's innodb_large_prefix as a possible workaround, which is default in 10.2 https://t.co/URwAEaZcN7
The reason is because MariaDB imposes a maximum of 767 bytes for indexes, and 767 / 4 = 191 (rounded down).
The danger of no Primary Key when replicating in RBR (partial protection with MariaDB 10.1) https://t.co/M6mABJdkmn by @jfg956