Every app is assigned to a Usage Plan which specifies the API rate limits. API rate limits ar specified per API group. Each API is assigned to to an API group and the combination of usage plan and API group determines the API rate limit. The actual limits for your app are listed in the Developer Portal app page under Rate Limits.
A Usage Plan is a set of API rate limits per API group. Every application is assigned a usage plan which enables consistent and efficient load allocation through correct use of the RingCentral Connect Platform.
RingCentral APIs are categorized by Usage Plan API Group which includes the following categories: Light, Medium, Heavy, and Auth.
Rate Limits is per API group. If your app is accessing multiple endpoints in the same API group, the requests are cumulative across endpoints. For example, if your app as a limit of 10 requests per minute for Heavy APIs and you make 5 each requests across 2 Heavy endpoints, you will be at your 10 requests per minute limit.
If you exceed the API rate limit, the server will return the 429 HTTP error status code indicating Too Many Requests. This means that the client is being throttled by the server due to high request rate. The Retry-After response header will specify the number of seconds that should elapse before your app can make requests again.
Here is the RingCentral API Rate Limit page which includes almost everything about rate limit: http://ringcentral-api-docs.readthedocs.io/en/latest/rate_limits/
Here is an article about RingCentral message storage and account data retention: https://success.ringcentral.com/articles/RC_Knowledge_Article/2178
According to this article: https://success.ringcentral.com/articles/RC_Knowledge_Article/2178, call recordings are retained 90 days for Non-HIPAA Accounts and 30 days for HIPAA Accounts.