Drupal Commerce Kickstart 2 Mysql problem: "Table XYZ is marked as crashed and should be repaired"
I have run into this problem a few times. It is indeed not directly Drupal related. However, since we are looking at MySQL through a Drupal lens, I guess we might as well answer it here.

The real source of the problem is a performance problem for your MySQL server. Drupal might have contributed to the problem by adding too much load. When I ran into a similar problem, I found out that a module I had written was making a huge amount of inserts into the access_log table, which then caused the table (and sometimes other tables) to crash. I ended up migrating to stronger hardware, which made the problem occur less frequently. Then I cleaned up my code to insert only what I really needed and the problem was gone.

I suspect, you will probably see this problem first on the tables that have the fastest growth rate. If so, take a look at which Drupal module inserts into them and find out, if you can optimize your insert strategy. If you can't, you might have to move your MySQL server to a separate machine or upgrade the hardware you are running on.