Pyrogram send_message method intermittently slow

Question

I am using the method send_message from Pyrogram to send messages to our users on Telegram. Sometimes it takes a while to finish its execution (up to 15 seconds) and some other times it works really fast (less than 1 second).

Is it a characteristic of the Telegram MTProto API or is there a way to keep the send_message method always fast?

Note: Tgcrypto is installed

Below is a code snippet showing the script:

from pyrogram import Client

app = Client(
    settings.TELEGRAM_BOT_NAME,
    api_id=settings.TELEGRAM_API_ID,
    api_hash=settings.TELEGRAM_API_HASH,
    bot_token=settings.TELEGRAM_BOT_TOKEN,
    in_memory=True
)
with app:
    while True:
        msg = Message.objects.next_to_send()
        response = app.send_message(msg.contact._id, msg.text) # Might take a while.
        sleep(2)

On every 2 seconds the script looks for a new message in our Database and send it to Telegram.

Thanks in advance,

Rhenan