Index both foreign keys in junction table. Consider composite primary key. Denormalize for read-heavy workloads.

Index both foreign keys in junction table

Use composite index on (fk1, fk2)

Consider covering indexes

Denormalize for read-heavy scenarios

Partition large junction tables

Forgetting to index junction table foreign keys

Not using composite primary key

Trying to model many-to-many without junction table

Not handling duplicate relationships

Missing metadata that should be in junction table