There is a limit of 600 /createMessage requests per minute for all Public accounts. In other words, you should not send more than 10 requests per second during one minute.
On the other hand, you can send 600 notifications in one request and then wait for a minute to send another one. The notification, in this case, will be counted as an individual request.
If it will be more than 600 notifications per minute, you will get "QUOTA_EXCEEDED" API response, and such requests will not be processed by our servers.
To get rid of this limitation and upgrade your account please contact us and we'll guide you through all necessary steps!