# foreign-keys

Published articles for foreign-keys.

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## Foreign keys are not overhead, and the thing you measured was a missing index

DevFeed: [Foreign keys are not overhead, and the thing you measured was a missing index](<https://devfeed.tech/articles/foreign-keys-are-not-overhead-and-the-thing-you-measured-was-a-missing-index-39597.md>)

Original publisher: [Read original article](<https://ankit-rana.com/logs/45-foreign-keys-are-not-overhead/>)

Author: hello@ankit-rana.com

Published: 2026-08-30T00:00:00Z

Content type: opinion

Language: en

Sources: [Ankit Rana | Mechanical Sympathy](<https://devfeed.tech/sources/ankit-rana-mechanical-sympathy.md>)

Topics: [Database](<https://devfeed.tech/topics/database.md>), [integrity](<https://devfeed.tech/topics/integrity.md>)

Tags: [database](<https://devfeed.tech/tags/database.md>), [database-performance](<https://devfeed.tech/tags/database-performance.md>), [foreign-keys](<https://devfeed.tech/tags/foreign-keys.md>), [indexing](<https://devfeed.tech/tags/indexing.md>), [integrity](<https://devfeed.tech/tags/integrity.md>), [overhead](<https://devfeed.tech/tags/overhead.md>), [postgres](<https://devfeed.tech/tags/postgres.md>), [postgresql](<https://devfeed.tech/tags/postgresql.md>), [referential-integrity](<https://devfeed.tech/tags/referential-integrity.md>), [schema-design](<https://devfeed.tech/tags/schema-design.md>)

### AI overview

The article explains that the measured cost of a slow parent delete is usually caused by a missing index on the child table's foreign-key column, not by foreign-key checking itself. It argues that dropping the constraint merely moves referential-integrity enforcement into application code and can allow orphaned records.

### Source excerpt

A foreign key check is an index lookup against a primary key that is almost certainly already in cache, which is close to the cheapest thing a database does. The expensive case people measure is a parent delete with no index on the child's referencing column, which forces a full scan of the child table per deleted row, and that is a missing index rather than a cost of the constraint. Dropping the key does not remove the work, it moves the integrity guarantee into application code where nothing reports when it stops holding.

## Soft deletes affect database constraints, indexes, and application queries

DevFeed: [Soft deletes affect database constraints, indexes, and application queries](<https://devfeed.tech/articles/soft-deletes-are-a-schema-decision-that-breaks-every-query-you-write-afterwards-39592.md>)

Original publisher: [Read original article](<https://ankit-rana.com/logs/40-soft-deletes-schema-decision/>)

Author: hello@ankit-rana.com

Published: 2026-08-20T00:00:00Z

Content type: opinion

Language: en

Sources: [Ankit Rana | Mechanical Sympathy](<https://devfeed.tech/sources/ankit-rana-mechanical-sympathy.md>)

Topics: [data-processing](<https://devfeed.tech/topics/data-processing.md>), [Database](<https://devfeed.tech/topics/database.md>), [MySQL](<https://devfeed.tech/topics/mysql.md>)

Tags: [data-modelling](<https://devfeed.tech/tags/data-modelling.md>), [database-design](<https://devfeed.tech/tags/database-design.md>), [foreign-keys](<https://devfeed.tech/tags/foreign-keys.md>), [indexes](<https://devfeed.tech/tags/indexes.md>), [indexing](<https://devfeed.tech/tags/indexing.md>), [mysql](<https://devfeed.tech/tags/mysql.md>), [orm](<https://devfeed.tech/tags/orm.md>), [postgresql](<https://devfeed.tech/tags/postgresql.md>), [predicate](<https://devfeed.tech/tags/predicate.md>), [schema](<https://devfeed.tech/tags/schema.md>), [schema-design](<https://devfeed.tech/tags/schema-design.md>), [soft-delete](<https://devfeed.tech/tags/soft-delete.md>)

### AI overview

The article explains how soft deletion affects database design beyond adding a deleted_at column. It discusses duplicate-key failures, foreign-key behavior, queries that may return deleted rows, and index inefficiency, noting that PostgreSQL partial indexes help while MySQL requires a workaround.

### Source excerpt

A deleted_at column turns every future query into a conditional one, and the cost is not the extra predicate. Unique constraints stop working because the deleted row still occupies the key, foreign keys start pointing at rows the application considers gone, and any query written by someone who does not know about the column silently returns deleted data. Soft delete is a data lifecycle decision, and treating it as a boolean column is what makes it expensive.