What is better to use?

Question

MySQL

Hello everyone, please tell me:
1) what is better to use for the ad aggregator, MyISAM or InnoDB
2) I look at two opencart and wordpress databases, I see opencart written in MyISAM, and WP on InnoDB, it is clear that there are no foreign keys in MyISAM and opencart did not use them , and why in WP there are no external relations?
3) and such a general question if you choose InnoDB, do you need to use foreign keys ?, again, I look at WP and don’t see external ones there, but instead of keys, indexes were used there, which is better?
I would be grateful for any advice!

Answer 1

standard question.
it all depends on the ratio of the number of select operations to the number of update/insert/delete operations.
you can even draw up graphs, the dependence of the average sampling time on the volume of the table and the ratio of the number of types of operations