GitHub Apps have a rate limit for requests.
Note: GitHub Apps are only compatible with the REST API v3 at this time.
GitHub Apps use the installation's minimum rate limit of 5,000 requests per hour. Organization installations with more than 20 users receive another 50 requests per hour for each user. Installations that have more than 20 repositories receive another 50 requests per hour for each repository.
For more detailed information about rate limits in the REST API v3, see "Rate limiting."