[API reference](https://evolu.dev/docs/api-reference) › [@evolu/common](https://evolu.dev/docs/api-reference/common) › [local‑first/Schema](https://evolu.dev/docs/api-reference/common/local-first/Schema) › SystemColumns

```ts
const SystemColumns: object({
  createdAt: DateIso,
  updatedAt: DateIso,
  isDeleted: /*#__PURE__*/ nullOr(SqliteBoolean),
  ownerId: OwnerId,
});
```

Defined in: [packages/common/src/local-first/Schema.ts:164](https://github.com/evoluhq/evolu/blob/e7144e2bbe9069362b62dec1b64a8aa922b8f1b0/packages/common/src/local-first/Schema.ts#L164)

System columns that are implicitly defined by Evolu.

- `createdAt`: Set by Evolu on row creation, derived from Timestamp.
- `updatedAt`: Set by Evolu on every row change, derived from Timestamp.
- `isDeleted`: Soft delete flag created by Evolu and used by the developer to
  mark rows as deleted.
- `ownerId`: Represents ownership and logically partitions the database.