> ## Documentation Index
> Fetch the complete documentation index at: https://docs.twenty.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Overview
> Shape the data your app adds to a workspace — objects, fields, and relations.
A Twenty app's **data layer** is the data your app *adds* to a workspace — the new record types it declares, the columns it adds to existing objects, and how those records connect to each other.
```text theme={null}
┌──────────────────────────────────────────────────┐
│ Object — a record type, e.g. PostCard │
│ ├─ Field (name, type, label) │
│ ├─ Field │
│ └─ Relation (link to another object) │
└──────────────────────────────────────────────────┘
│
├── lives in your app, OR
│
▼
┌──────────────────────────────────────────────────┐
│ Standard / other apps' objects │
│ └─ Field added by your app via defineField │
└──────────────────────────────────────────────────┘
```
## In this section
`defineObject` — declare new record types with their own fields.
`defineField` — add fields to standard or other apps' objects.
Bidirectional `MANY_TO_ONE` / `ONE_TO_MANY` connections between objects.
## Entities at a glance
| Entity | Purpose | Defined with |
| ------------ | ----------------------------------------------------------------------------------------------------------------- | ----------------------------------------- |
| **Object** | A new custom record type (e.g. PostCard, Invoice) with its own fields | `defineObject()` |
| **Field** | A column on an object. Standalone fields can extend objects you didn't create (e.g. add `loyaltyTier` to Company) | `defineField()` |
| **Relation** | A bidirectional link between two objects — both sides declared as fields | `defineField()` with `FieldType.RELATION` |
| **Index** | A database index to speed up a recurring query on one of your objects | `defineIndex()` |
The SDK detects these via AST analysis at build time, so file organization is up to you — the convention is `src/objects/`, `src/fields/`, and `src/indexes/`. Stable `universalIdentifier` UUIDs tie everything together across deploys.
## Indexes (optional)
Apps can ship indexes alongside their objects to keep recurring queries fast. The most common case is a status or foreign-key column that you read frequently.
```ts src/indexes/post-card-status.index.ts theme={null}
import { defineIndex } from 'twenty-sdk/define';
import {
POST_CARD_UNIVERSAL_IDENTIFIER,
STATUS_FIELD_UNIVERSAL_IDENTIFIER,
} from '../objects/post-card.object';
export default defineIndex({
universalIdentifier: 'b6e9d2a1-5a4c-46ca-9d52-42c8f02d1ff0',
objectUniversalIdentifier: POST_CARD_UNIVERSAL_IDENTIFIER,
fields: [
{
universalIdentifier: 'b6e9d2a1-5a4c-46ca-9d52-42c8f02d1ff1',
fieldUniversalIdentifier: STATUS_FIELD_UNIVERSAL_IDENTIFIER,
},
],
});
```
### Unique indexes
`defineIndex` accepts `isUnique: true` for both single- and multi-column uniqueness. This is the recommended primitive — `defineField({ isUnique: true })` is deprecated and will be removed in a future release.
```ts theme={null}
defineIndex({
universalIdentifier: '…',
objectUniversalIdentifier: PERSON_UNIVERSAL_IDENTIFIER,
isUnique: true,
fields: [{ universalIdentifier: '…', fieldUniversalIdentifier: EMAIL_FIELD_UNIVERSAL_IDENTIFIER }],
});
```
### Other constraints
* Partial `WHERE` clauses stay under admin control — apps can't declare them.
* Each object is capped at 10 custom indexes (the framework's own indexes don't count).
Order the `fields` array the way Postgres should use it — leftmost column first, like a phone book. Indexes are not free: every write to the table updates them. Add one only when you have a query that needs it.
Looking for **Application Config** or **Roles & Permissions**? Those describe the app itself rather than the data it adds — they live under [Config](/developers/extend/apps/config/overview). Looking for **Connections** (Linear, GitHub, Slack OAuth)? Those exist to be called *from* logic functions and live under [Logic](/developers/extend/apps/logic/connections).