Slow site with ~1,000 blog posts?

Thank you.

The graph is from Uptime Kuma and displays a simple response time.

I’ve read the Performance and Caching material and am using the default caching.

From system.yaml:

cache:
  enabled: true
  check:
    method: file
  driver: auto
  prefix: g
  purge_at: '0 4 * * *'
  clear_at: '0 3 * * *'
  clear_job_type: standard
  clear_images_by_default: true
  cli_compatibility: false
  lifetime: 604801
  gzip: true
  allow_webserver_gzip: false
  redis:
    socket: null
    password: null
    database: null
    server: null
    port: null
  memcache:
    server: null
    port: null
  memcached:
    server: null
    port: null
twig:
  cache: true
  debug: false
  auto_reload: true
  autoescape: false
  undefined_functions: true
  undefined_filters: true
  safe_functions: {  }
  safe_filters: {  }
  umask_fix: false

and

flex:
  cache:
    index:
      enabled: true
      lifetime: 60
    object:
      enabled: true
      lifetime: 600
    render:
      enabled: true
      lifetime: 600

An older post suggests that 1,000 pages was the limit. However, with Grav 1.7+, this doesn’t seem like an issue. (We’re on Grav 1.7.48.)

I’m trying to figure out why removing these posts would have such a marked difference in the responsiveness of the site.