AWS Polly python synthesize_speech delayed response

I'm not sure if I'm doing things incorrectly, but sometimes it takes almost precisely a minute (60-61 secs) to get a response back. Most of the time it is < 1 sec, but sometimes it gets to 60.x secs - never longer, never shorter, always around that 1 minute mark. Some background:
I'm using it in a Django application, and in a helper file, towards the top I initiate things:

session = Session(
        region_name="us-east-1",
        aws_access_key_id=...
        aws_secret_access_key=...
        )
polly = session.client("polly")

Then down in a function (in the helper file):

def some_function():
    time1 = time.time()
    response = polly.synthesize_speech(
                            Text=<....>,
                            OutputFormat="mp3",
                            VoiceId="Justin",
                            TextType="ssml"
                        )
    time2 = time.time()

Then in a views file (since this is used in Django), it will call on "some_function" when requests arrive.

As mentioned, time2 - time1 is usually < 1 sec, but from time to time, it gets to 60-61 secs... I initially thought it was some sort of rate limiting, but I looked up the limits for AWS polly and it seems like I am far away from any throttling limits. I'm out of ideas, so any inspiration is much welcome! Thanks in advance!

Also, not sure if relevant, but the Django app is hosted on Azure - would that cause any random in occurrence, but consistent in duration delays?