Create opinionated PostgreSQL sizing guidelines for Red Hat Developer Hub (RHDH) to help users properly size their external database deployments based on their workload requirements.

This work is continuing on the initial external DB support epic (https://issues.redhat.com/browse/RHIDP-2016)

The goal is to finish tasks that we were not able to do in the previous epic (like sizing guidelines), and to improve the documentation on external db configuration.

Background/Feature Origin

Performance testing of RHDH v1.4+ revealed significant resource usage changes compared to v1.3 (35% more memory, 15% more storage). Current documentation lacks specific PostgreSQL sizing guidance, leaving users to guess appropriate database resources for their deployment scale. e.g.: https://docs.redhat.com/en/documentation/red_hat_developer_hub/1.6/html/about_red_hat_developer_hub/rhdh-sizing_about-rhdh lacks sizing guidelines

and https://docs.redhat.com/en/documentation/red_hat_developer_hub/1.6/html/configuring_red_hat_developer_hub/configuring-external-postgresql-databases lacks a Reference to sizing guidelines, a cross-link to the sizing section would be appreceated. 

Why is this important?

Prevents under-provisioning: Users avoid performance issues and failures due to insufficient database resources

Cost optimization: Users can right-size their PostgreSQL deployment without over-provisioning

Deployment confidence: Clear guidelines reduce uncertainty when planning RHDH deployments

Scalability planning: Users understand resource requirements as they grow their RHDH usage

User Scenarios

Platform Administrator planning initial RHDH deployment needs to determine appropriate PostgreSQL instance size

Database Administrator configuring external PostgreSQL for RHDH wants specific CPU, memory, and storage recommendations

Operations Team scaling existing RHDH deployment needs guidance on when to upgrade database resources

Enterprise Customer with 2,000+ users requires PostgreSQL sizing for large-scale deployment with HA considerations

Dependencies (internal and external)

• Internal: Performance & Scale team test results and recommendations
• Internal: Documentation team for official documentation creation
• External: Customer feedback on real-world usage patterns
• External: PostgreSQL best practices and sizing methodologies

Acceptance Criteria

• Analysis Complete: Document analysis of performance test results from v1.4 vs v1.5 etc see: https://docs.google.com/document/d/1oaUe1KOjV9MH8ITizZ1Wu-lwqupC1qvjE0ce9cx24Qg/edit?tab=t.0
• Sizing Matrix Create: Define PostgreSQL sizing recommendations table and provide the relevant content and context.
• Draft Guidelines: Create technical draft of sizing guidelines ready for documentation team
• (i)Stakeholder Review: Technical review completed with Performance & Scale, rhdh engineers and Documentation teams.