Kysely Query Architect

Type-safe Kysely queries use explicit column selection with `.select([...])` and let Kysely infer return types automatically. Create query classes in `@packages/db/src/queries/*.ts` that inject a `Kysely<Database>` instance and return `.execute()` results, ensuring compile-time type safety without manual type annotations.

Compose query classes by injecting them as dependencies into other classes, allowing shared query logic for dashboards and modules. This pattern centralizes query builders and prevents duplication while maintaining type safety across your TypeScript project.

Use Common Table Expressions (CTEs) and joins to structure complex queries efficiently, and parallelize independent queries with `Promise.all()`. Database-side logic for aggregations, filtering, and sorting reduces data transfer and improves execution speed.

Yes. Kysely infers query result types from explicit column selections, eliminating manual type annotations. Define your database schema once as `Kysely<Database>`, and type inference handles the rest across all query methods.

Always prefer `.select([...])` to explicitly declare which columns you need. This improves query performance, reduces data transfer, makes dependencies explicit, and ensures type safety by preventing accidental exposure of sensitive or unused columns.

Organizing queries into dedicated classes by domain (e.g., SalesQueries, UserQueries) centralizes related logic, enables dependency injection for reuse, supports team collaboration, and makes queries easier to test, maintain, and optimize across TypeScript projects.