A 429 error means that the API key in question has a rate limit placed on it by you: https://www.algolia.com/doc/guides/security/api-keys/in-depth/api-key-restrictions/#rate-limit
You can check the rate limit you have set by looking up the key in question in the API keys section of your Algolia Dashboard: https://dashboard.algolia.com/account/api-keys/restricted
Please note that this will only work for users with access to the key in question.
You can adjust the rate limit to a higher value to avoid seeing the error, the value you set is the number of request you expect to receive from a single IP address in a one hour period.