To optimize the key_buffer_size, you need to review the key_read statistics: MariaDB [(none)]> SHOW STATUS LIKE “key%”; +————————+———+ | Variable_name          | Value   | +————————+———+ | Key_blocks_not_flushed | 0       | | Key_blocks_unused      | 1428301 | | Key_blocks_used        | 4187    | | Key_blocks_warm        | 0       | | Key_read_requests      | 82847   | | Key_reads              | 4187    | | ...