To mitigate the effect of bots on your Algolia usage you can generate a new Search API Key with limited queries per hour and per IP address: Rate Limiting an API Key. This can be used to potentially prevent overage charges. You can follow the steps on the doc How can I rate limit an API key? to set a limit.
The limit is up to you; we generally recommend starting with a higher number ( to avoid limiting real users) and reducing it gradually based on the impact of bots.
The rate limit does not stop the request completely as it is hard to do so without blocking genuine traffic. If you were to block specific IP addresses the bot can change these to avoid any block put in place.
The idea with a rate limit is to find a level where it's prohibitive for bots to abuse or scrape your site. As long as your site is publicly viewable, without requiring users to sign in, there will always be some bot potential where users can submit information.
If you need help to implement this feature you can contact our support team through the Support Center.