Prometheus system requirements

Looking for best practices on system requirements to configure Prometheus on a VM.

Sizing recommendations as below

  1. CPU
  2. Memory
  3. Storage

We built a 4 VM Prometheus cluster backed by Thanos for HA.
however after configuring the Datastax(Cassandra) servers as one of it targets to scrape metrics, Prometheus services are utilizing high CPU and Memory with process crash and restarts.

it would be a great help for us in getting Ideas/suggestions from you!!
please let me know for any more details, happy to provide