The absolute fastest way to create a serverless Twilio incoming call webhook Lambda:

npm install -g serverless
sls install --url https://github.com/revmischa/slspy --name twilcall
echo "twilio" > requirements.txt

---

handler.py:

from twilio.twiml.voice_response import VoiceResponse
from urllib.parse import parse_qsl


def hello(event, context):
    call = dict(parse_qsl(event['body']))

    resp = VoiceResponse()
    resp.say("hello world!", voice='alice')

    response = {
        "headers": {"content-type": "text/xml"},
        "statusCode": 200,
        "body": str(resp),
    }

    return response

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Deploy, then set webhook handler for your phone number:

sls deploy

That’s all!

Customize your response with TwiML.

See this gist to check out more advanced handling with loading the Twilio API key from Secrets Manager, doing lookups with Twilio Add-Ons to detect spam/robocalling, and detailed caller lookup info that is output to a slack channel every call.