i want to know the limit request on etherscan API with API key, and limit if we go on paid service. thanks in advance.
The number of requests per second is limited to 5 request per second. There is not paid service yet.
The Etherscan Ethereum Developer APIs are provided as a community service and without warranty, so please just use what you need and no more. They support both GET/POST requests and a rate limit of 5 requests/sec.
To use the API service please create a FREE Api-Key Token from within the ClientPortal->MyApiKey area which you can then use with all your api requests. Either a link back or mention that your app is "Powered by Etherscan.io APIs" would be appreciated.
Hope this helps