Cheapest way to host a real-time Covid appointment finder website

Building something similar to https://impftermin.berlin/.

This site does 400K hits monthly, (using a polling interface every 5s to an API).

The functionality is:

- Scrape Doctolib, KV Berlin on an interval for appointment slots

- Show appointment slots on website

- Push updates to users in real-time

The full (un-optimized) scraped dataset of appointments is 1.5MB.

What hosting providers (vercel, render, ec2, etc.), programming languages (node, rust, go, etc.), hosting strategy (ssr, static page, spa), transport ( websockets, server-sent events, polling), frameworks (next.js, blitz, hasura, etc.) would suit this task the best?

I want to host it as cheap as possible.

Low development/maintenance effort is also important.