Databases Skill Unified guide for working with MongoDB (document-oriented) and PostgreSQL (relational) databases. Choose the right database for your use case and master both systems. When to Use This Skill Use when: - Designing database schemas and data models - Writing queries (SQL or MongoDB query language) - Building aggregation pipelines or complex joins - Optimizing indexes and query performance - Implementing database migrations - Setting up replication, sharding, or clustering - Configuring backups and disaster recovery - Managing database users and permissions - Analyzing slow queries…