database

While ActiveRecord validations catch most invalid data, database constraints provide a safety net that prevents invariant violations even when validations are bypassed. I add null: false constraints for required columns, unique indexes for uniqueness

Bulk operations reduce database round-trips dramatically. I use bulk_create() for inserting many objects at once, bulk_update() for updates, and update() for queryset-level updates. These bypass save() methods and signals for speed. For large datasets

Spring's @Transactional manages database transactions declaratively. Transaction propagation controls behavior when methods call other transactional methods—REQUIRED, REQUIRESNEW, NESTED. Isolation levels prevent concurrent access issues—READUNCOMMITT

Migrations evolve database schema safely across environments. I follow strict conventions: one logical change per migration, descriptive names, reversible operations. Using change instead of up/down enables automatic rollback for most operations. For

As applications grow, read operations often dominate database load. Directing reads to replica databases while keeping writes on the primary reduces contention and improves response times. Rails makes this straightforward with connects_to and role-bas

Migrations track database schema changes. I use makemigrations after model changes and review generated migrations. For data migrations, I create empty migrations with makemigrations --empty and write RunPython operations. I test migrations on dev dat

Database routers enable read-write splitting for scaling. I direct reads to replicas and writes to primary. The router examines hints and model to make routing decisions. For read-heavy apps, this distributes load across multiple databases. I use usin

The only() method loads specified fields only, while defer() excludes specified fields. This reduces data transfer and memory usage. I use only() when I need just a few fields from large models. For read-only displays, this prevents loading unnecessar

Connection pooling reuses database connections instead of creating new ones per request. I use django-db-pool or configure persistent connections with CONN_MAX_AGE. This reduces connection overhead significantly. For high-traffic sites, I set appropri

SQL joins combine data from multiple tables. INNER JOIN returns matching rows only. LEFT/RIGHT JOIN includes all rows from one table, nulls for non-matches. FULL OUTER JOIN combines both. I use CROSS JOIN for Cartesian products sparingly—performance k

Normalization eliminates redundancy and anomalies. 1NF requires atomic values—no arrays in columns. 2NF eliminates partial dependencies—all non-key columns depend on entire primary key. 3NF removes transitive dependencies—non-key columns don't depend

Sqlx is a pure-Rust SQL client that checks queries at compile time against your database schema. The query! macro connects to your DB during compilation and validates that columns and types match. This catches typos and schema drift before runtime. It