I have read that the insert performance for UUID as a primary_key depends on how many records exists in the database. With the greater number of records the more time it taking to insert records
https://kccoder.com/mysql/uuid-vs-int-insert-performance/
The author for the above article has run experiments, he thinks its because there are greater number of reads for UUID primary_key insert than other auto incremented integers.
I wanted to ask whether databases automatically create an index for the the chosen primary_key If the UUID primary_key index is the problem, would the insert problem be solved by using an integer as the primary_key index while still keeping the UUID field, then switching the primary keys to UUID, the problem then is would the foreign key references to integer ID propagate to the UUID field upon the switching?