mysqltuner - Write Key buffer hit rate I'm pasting section of MySQL Tuner result regarding MyISAM Metrics.
[OK] Currently running supported MySQL version 5.5.57-0ubuntu0.14.04.1-log
[OK] Operating on 64-bit architecture

-------- Performance Metrics -----------------------------------------------------
[--] Up for: 25d 1h 40m 20s (6M q [3.149 qps], 170K conn, TX: 15G, RX: 1G)
[--] Reads / Writes: 90% / 10%

-------- MyISAM Metrics ----------------------------------------------------------
[!!] Key buffer used: 20.1% (80M used / 402M cache)
[OK] Key buffer size / total MyISAM indexes: 384.0M/31.6M
[OK] Read Key buffer hit rate: 99.9% (7M cached / 4K reads)
[!!] Write Key buffer hit rate: 1.2% (2M cached / 25K writes)

I'm looking for way to improve or optimize the Write Key buffer hit rate. Or why is it so bad?
I don't know which server variables may play role in this result, so please let me know what variables should I paste here or if you need any specific details.
Thanks for help!
UPDATE 2017-08-11 13:56 CET
I did some more tests based on recommendations from @RolandoMySQLDBA and it really seems I should not worry about this metric. After I lowered the key_buffer_size, the Write buffer key hit rate improved directly. However, I couldn't measure any improvement in speed of reads. I assume it's because there was not enough memory for cache, so almost all writes went through. I still don't really understand what is the good or bad thing about Write buffer key hit rate, but it seems to be related to optimal size of key buffer based on the data and index in database.
OK, the hit rate is low.  But let's put things in perspective...  25K writes in 25 days is so insignificant (&lt; 1/minute) as to be the least of your worries.  5K/minute would be a concern.

If you are having performance problems, locate the slowest query and study it -- its indexes, its formulation, etc.

The "key buffer" applies to MyISAM tables, of which you have only 1.  The InnoDB statistics are not listed.

For further discussion, see http://mysql.rjweb.org/doc.php/mysql_analysis