Slow queries : Index 'mdl_sess_tim2_ix' on table 'mdl_sessions' and column 'timemodified'

Hello,

We have some slow queries on one of our Moodle platform.

The 'mdl_sessions' table has ~5000 rows, and each time it's updated, this leads to a slow query (we think because of the index mdl_sess_tim2_ix (timemodified)).

Why is there an index on timecreated and timemodified for this table ?

Can we remove them ?

Thank you in advance for you answer.

Kind regards,

Olivier