database

Database routers direct queries to specific databases. I implement db_for_read(), db_for_write(), allow_relation(), and allow_migrate() methods. This enables read replicas, sharding by model, or separating analytics data. The router checks model label

The N+1 query problem is Django's most common performance trap. I use select_related for foreign key and one-to-one relationships (performs SQL JOIN), and prefetch_related for many-to-many and reverse foreign keys (separate queries with Python join).

Indexes dramatically improve query performance. I add indexes via Meta.indexes or db_index=True on frequently-filtered fields. Compound indexes help queries filtering on multiple fields. For text search, I use GinIndex on PostgreSQL. I index foreign k

Model Meta class controls database behavior. I use ordering for default query ordering, indexes for database indexes, and unique_together for composite uniqueness constraints. The db_table option customizes table names. For large tables, managed=False

Database indexes dramatically speed up queries. I add indexes to frequently-filtered fields via db_index=True or Meta.indexes. Compound indexes help queries filtering on multiple fields together. For text search on PostgreSQL, I use GinIndex with Sear

select_for_update() locks rows until transaction completes, preventing race conditions. I use it for operations requiring read-modify-write atomicity like decrementing stock or updating counters. The lock is released on transaction commit/rollback. Fo