Add captcha or token to searchController

[MarioXP]

Hi,
lately my site is under DDOS attacks like sitename.it/search?controller=search&s=QQQQQQQQ
made from different IP addresses, and with different search keys, like:
AAAAAA, BBBBBB, QQQQQQ, etc. etc.

This causes slowdowns and in some cases the blocking of mysql.

In your opinion, is it better to insert a recaptcha on the search form (not very usable) or is there any other security measure to prevent direct calls to the controllers/front/listing/SearchController.php from outside?

I was thinking of a token.
Is anyone ever in this situation?
I use the last PrestaShop version (1.7.6.5)

Thank you