In the Rest API, Rate Limiting is enabled and you're limited to 600 requests pr. rolling 60 seconds.
In the response of any request, a few headers will be added to tell what your current limit is, and how many requests you have remaining.
X-RateLimit-Limit : 600 X-RateLimit-Remaining : 599
If you exhaust your ratelimit, an additional header will be provided to tell when your ratelimit is reset.