Azure FaceAPI limits iteration to 20 items - azure

Question

I have a list of image urls from which I use MS Azure faceAPI to extract some features from the photos. The problem is that whenever I iterate more than 20 urls, it seems not to work on any url after the 20th one. There is no error shown. However, when I manually changed the range to iterate the next 20 urls, it worked.
Side note, on free version, MS Azure Face allows only 20 requests/minute; however, even when I let time sleep up to 60s per 10 requests, the problem still persists.
FYI, I have 360,000 urls in total, and sofar I have made only about 1000 requests.
Can anyone help tell me why this happens and how to solve this? Thank you so much!
# My codes
i = 0
for post in list_post[800:1000]:
i += 1
try:
image_url = post['photo_url']
headers = {'Ocp-Apim-Subscription-Key': KEY}
params = {
'returnFaceId': 'true',
'returnFaceLandmarks': 'false',
'returnFaceAttributes': 'age,gender,headPose,smile,facialHair,glasses,emotion,hair,makeup,occlusion,accessories,blur,exposure,noise',
}
response = requests.post(face_api_url, params=params, headers=headers, json={"url": image_url})
post['face_feature'] = response.json()[0]
except (KeyError, IndexError):
continue
if i % 10 == 0:
time.sleep(60)

Answer 1

The free version has a max of 30 000 request per month, your 356 000 faces will therefore take a year to run.
The standard version costs USD 1 per 1000 requests, giving a total cost of USD 360. This option supports 10 transactions per second.
https://azure.microsoft.com/en-au/pricing/details/cognitive-services/face-api/