Ask HN: A client project is getting momentum, I need infrastructure advices

First off, I am by no means an infrastructure or devops guys, I'm a senior nodejs freelance, so some of this is new to me

This is the current infrastructur:e

- A nginx reverse proxy in front of the nodejs API VPS

- A 24 vCPU, 128 GB VPS

- A 64GB, 8vCPU database

- The landing page is on a Cloudflare worker

I am using PM2 to start a nodejs instance on each vCPU, so we have 24 instances of the API running behind the pm2 load balancer, itself behind the nginx reverse proxy

We're expecting around 50M-70M requests for next sunday, with most requests received around 9pm, we are expecting around 90k concurrent users

We are not using sockets, only HTTP requests (GET, POST, PUT)

I am looking for infrastructure tips to make sure that the API hold the traffic

Do you have any advice or tips on how I can scale the infrastructure and make sure that the API holds this kind of traffic ?

Thank you