With Heroku removing free tiers it's natural to seek free alternatives. AWS has a free tier with generous limits. Serverless setup with Lambdas is free for a year and cheap afterward. Resources are only allocated when your bot is triggered, so we need to setup a webhook. There are plenty of articles on how to do that, basically, run

curl -GET https://api.telegram.org/bot{BOT_TOKEN}}/setWebhook?url={GATEWAY_URL | FUNCTION_URL}

However, AWS Lamda currently doesn't support async invocations for Python, and with PTB v20.x we should work around that. To make it work, feel free to use the following example:

import asyncio
from telegram.ext import Application

application = Application.builder().token(TELEGRAM_API_KEY).build()


def lambda_handler(event, context):
    return asyncio.get_event_loop().run_until_complete(main(event, context))

async def main(event, context):
    # Add conversation, command, and any other handlers
    
    try:    
        await application.initialize()
        await application.process_update(
            Update.de_json(json.loads(event["body"]), application.bot)
        )
    
        return {
            'statusCode': 200,
            'body': 'Success'
        }

    except Exception as exc:
        return {
            'statusCode': 500,
            'body': 'Failure'
        }

Lambda setting for Code / Runtime Settings / Handler should point to {main_file}.lambda_handler, e.g. bot.lambda_handler

This asyncio pattern is far from ideal as described here, but it works as expected.