Have you worked directly with PostgreSQL?

Yes, I have worked directly with PostgreSQL. My experience includes:

• Writing and optimizing SQL queries for data retrieval and aggregation;
• Creating and modifying database schemas (tables, indexes, constraints);
• Configuring performance parameters such as memory settings and query planner;
• Using transactions and managing locks;
• Integrating PostgreSQL with applications via drivers and ORM;
• Backing up and restoring data.

For example, to optimize queries, I used EXPLAIN ANALYZE, created indexes on frequently used fields, and monitored table statistics.