In general, non-commercial users of our API can expect a rate limit of around 120 calls per minute. This may vary depending upon overall system activity. If we are under a light load we may increase the limit associated with your API key and conversely, if we are under heavy load we may reduce that limit.
You can inspect the response header to get more info. There are three fields in the header associated with rate limits:
X-RateLimit-Limit - the current rate limit for this API key
X-RateLimit-Used - the number of method calls used on this API key this minute
X-RateLimit-Remaining - the estimated number of remaining calls allowed by this API key this minute