> For the complete documentation index, see [llms.txt](https://docs.payments.thalescloud.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.payments.thalescloud.io/instant-issuance/integrate-d1-api/d1-api-reference/inbound-api-to-d1.md).

# Inbound API (to D1)

Inbound APIs are called by your **issuer backend** to perform operations in the **D1 backend**.

Use these APIs to:

* Authenticate to D1 and obtain an access token.
* Request physical card production (including instant issuance).

### Before you start

You need these integration building blocks in place:

* **TLS mutual authentication (mTLS)** between your issuer backend and the D1 backend.
* **OAuth 2.0 access tokens** to authorize calls to D1 APIs.
* **JWE encryption** for sensitive card data fields (for example, PAN).

Start here:

* [Set up TLS mutual authentication](/instant-issuance/integrate-d1-api/set-up-tls-mutual-authentication.md)
* [Get OAuth2.0 access token](/instant-issuance/integrate-d1-api/get-oauth2.0-access-token.md)
* [Encrypt sensitive data](/instant-issuance/integrate-d1-api/encrypt-sensitive-data.md)

### APIs in this section

<table data-view="cards"><thead><tr><th>API</th><th data-card-target data-type="content-ref">Reference</th></tr></thead><tbody><tr><td><strong>OAuth2 API</strong><br>Get an OAuth 2.0 access token for D1 API calls.</td><td><a href="/spaces/1qJ8OQRIA2FuYOSRgnR2/pages/uEzPy2u8gld2HQVB2BKi">/spaces/1qJ8OQRIA2FuYOSRgnR2/pages/uEzPy2u8gld2HQVB2BKi</a></td></tr><tr><td><strong>Physical issuance API</strong><br>Request physical card production (for example, central issuance or instant issuance).</td><td><a href="/spaces/1qJ8OQRIA2FuYOSRgnR2/pages/lHQdBIzJy5oOXYM5IvQJ">/spaces/1qJ8OQRIA2FuYOSRgnR2/pages/lHQdBIzJy5oOXYM5IvQJ</a></td></tr></tbody></table>

### Common call pattern

1. Call the OAuth2 API to obtain an access token.
2. Call the target D1 API with `Authorization: Bearer <access_token>`.
3. Reuse the token until it expires (15 minutes).

{% hint style="info" %}
Inbound and outbound connectivity both require mTLS.

OAuth 2.0 access tokens apply to inbound calls only (issuer backend to D1 backend).
{% endhint %}


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