---
title: "Upsert object"
method: POST
path: "/api/v1/cdp/custom-objects"
tags: ["CDP Custom Objects"]
---

# Upsert object

`POST /api/v1/cdp/custom-objects`

Create or update a custom object by type and external id. The type must already exist; free-form attributes are fully replaced.

## Request body

- object
  - `type` string, required — The custom object type name. Must already exist (create it with the types endpoint) — unknown types are rejected.
  - `externalId` string, required — Your stable identifier for this object within its type (idempotency key).
  - `displayName` string — Human-readable label for the object.
  - `attributes` object — Free-form custom traits (full-replace on upsert).

## Response `200`

Success

- object
  - `type` string, required
  - `externalId` string, required
  - `created` boolean, required

## Other responses

- `400` — Validation failed or the request cannot proceed.
- `401` — Missing, malformed, or revoked API key.
- `404` — The resource does not exist in this organization.
- `409` — Conflicts with the current state (duplicates, wrong lifecycle state).
- `422` — The request is well-formed but semantically invalid.
- `429` — Rate limit exceeded — retry after `Retry-After`.
- `500` — Internal server error.
- `503` — Transient error — retry with a narrower request.

---

[API](https://skmtc.net/useboom/apis/boom-api.md) · [All operations](https://skmtc.net/useboom/apis/boom-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/useboom/boom-api/revisions/00f873e07076/schema)