[jongs]

Indexing is on but my understanding is that it only help reading, not writing on the DB

[carbocation]

What you say is true; indexing does not make writes faster. In fact, it makes writing to the DB slower, which is why I suggested to turn it off. Now, there may be extenuating circumstances (e.g., you also read from this DB) which make this decision more difficult.

[jongs]

Why would it make it slower?

[carbocation]

Instead of just inserting a record, it now has to do something else, too (update the index).

Try taking a look at http://kevin.vanzonneveld.net/techblog/article/improve_mysql... , which suggests some things you can try. This might be a question better suited for StackOverflow, by the way.

[jongs]

thanks