What databases have you worked with and what exactly did you do?

In my practice, I have worked with several types of databases:

• PostgreSQL: designed and optimized schemas, wrote complex SQL queries and procedures, handled migrations and index tuning for performance.
• MySQL: participated in setting up replication, query optimization, and application integration.
• MongoDB: designed document structures, implemented aggregations, and ensured scalability.
• Redis: used as a cache and for implementing message queues.

Specifically, I was involved in analyzing data requirements, designing ER diagrams, optimizing queries, and ensuring data integrity.