Rate limiting of the API is primarily on a per-user basis — or more accurately described, per user API token. It allows 60 requests per minute per API token. On each request, your current rate limit status is returned in the response headers:
X-RateLimit-Limit: 60 X-RateLimit-Remaining: 55
If you get response code 429, it means that you have sent too many requests. If this happens, have a look in the Retry-After header, where you will see a number displayed. This is the amount of seconds that you need to wait, before you can retry sending your requests.