Docs on lowering node counts for 3k ref arch

doc/administration/reference_architectures/3k_users.md

@@ -2088,6 +2088,9 @@ but with smaller performance requirements, several modifications can be consider
 - Combining select nodes: Some nodes can be combined to reduce complexity at the cost of some performance:
   - GitLab Rails and Sidekiq: Sidekiq nodes can be removed and the component instead enabled on the GitLab Rails nodes.
   - PostgreSQL and PgBouncer: PgBouncer nodes can be removed and the component instead enabled on PostgreSQL with the Internal Load Balancer pointing to them instead.
+- Reducing the node counts: Some node types do not need consensus and can run with fewer nodes (but more than one for redundancy). Note that this will also lead to reduced performance.
+  - GitLab Rails and Sidekiq: Stateless services don't have a minimum node count. Two are enough for redundancy.
+  - Gitaly and Praefect: A quorum is not strictly necessary. Two Gitaly nodes and two Praefect nodes are enough for redundancy.
 - Running select components in reputable Cloud PaaS solutions: Select components of the GitLab setup can instead be run on Cloud Provider PaaS solutions. By doing this, additional dependent components can also be removed:
   - PostgreSQL: Can be run on reputable Cloud PaaS solutions such as Google Cloud SQL or AWS RDS. In this setup, the PgBouncer and Consul nodes are no longer required:
     - Consul may still be desired if [Prometheus](../monitoring/prometheus/index.md) auto discovery is a requirement, otherwise you would need to [manually add scrape configurations](../monitoring/prometheus/index.md#adding-custom-scrape-configurations) for all nodes.