Optimizing database queries in Node.js apps is essential for ensuring good performance, especially with large datasets. Start by creating indexes on frequently queried columns, as this can dramatically speed up search operations. Always limit the number of records returned by your queries, especially for large tables, to avoid unnecessary data transfer and memory usage. Using pagination or cursors for large result sets can help here. Additionally, implement connection pooling to efficiently manage database connections. Libraries like `pg-pool` for PostgreSQL or `mysql2` for MySQL provide built-in pooling capabilities that reduce the overhead of opening and closing database connections for every query. By optimizing queries and connection management, you ensure faster and more scalable database interactions.