Integrating RELM Checkout via Direct API

This guide explains how to integrate RELM Checkout directly into your e-commerce store or POS system using the RELM REST API.

Prerequisites

Before starting the integration, ensure that you have the following:

• Key ID, Public Key, and Private Key are generated as mentioned in the Reference
• Implemented API signature generation as described in the Authentication & Signing Guide
• Basic familiarity with HTTP requests and JSON payloads

Environment URLs

Use the following base URLs depending on the environment you are working in.

Environment	Base URL
Sandbox	https://sandbox.api.relm.co
Production	https://api.relm.co

Integration Steps

Step 1. Call the Order creation api to create an order on RELM System

Endpoint – /v1/pos/client/order/create

Method – POST

Headers

"header" : {
  "Content-Type" : "application/json"
  "Authorization" : "Signature {Generated Signature}"
}

Request

{
  "clientOrderId": "{Your specific order id}",
  "orderAmount": "{amount of the order}",
  "currencyCode": "{currency of the amount in FIAT}",
  "description": "{Description of the Cart}",
  "recipientEmail": "{customer email}",
  "redirectUrl": {
    "accept": "{Your accept Url for redirect}",
    "cancel": "{Your cancel Url for redirect}",
    "failed": "{Your failed Url for redirect}"
  }
}

Response

{
  "success": true,
  "data": {
    "orderId": "string",
    "clientOrderId": "string",
    "orderAmount": "string",
    "orderCurrency": "string",
    "recipientEmail": "string",
    "status": "string",
    "orderType": "string",
    "token": "string",
    "paymentCurrency": "string | undefined",
    "paymentAmount": "string | undefined",
    "payerPaidAmount": "string | undefined",
    "payerRemainingAmount": "string | undefined",
    "payerEmail": "string",
    "paymentWalletAddress": "string",
    "qrCode": "string",
    "paymentLink": "string",
    "company": "object | undefined",
    "network": "string",
    "createdAt": "Date",
    "expiresAt": "Date",
    "additionalInfo": "string | undefined",
    "payerConversionRate": "string | undefined"
  }
}

You will receive a paymentLink in the response, which you need to redirect the user to.

With this paymentLink, your frontend can navigate to our Checkout solution which will further process the order and receive the payment.

Rate Limiting

There are currently no rate limits enforced for creating orders via the RELM APIs. You can create orders as needed without restrictions.

Error Codes

When an error occurs, the API responds with a structured error object. Below is the general format:

{
  "success": false,
  "error": {
    "code": "string",
    "fullCode": "string",
    "msg": ["string"],
    "source": "string",
    "statusCode": "number",
    "traceId": "string"
  }
}

Example: 500 Internal Server Error

{
  "success": false,
  "error": {
    "code": "internal-server-error",
    "fullCode": "RELM-GEN-INTERNAL-SERVER-ERROR",
    "msg": [
      "\nInvalid `prisma.posOrder.create()` invocation:\n\n\nUnique constraint failed on the fields: (`clientOrderId`)"
    ],
    "source": "GEN",
    "statusCode": 500,
    "traceId": "cfc75450-1bba-11f1-ad67-93c03b26c699"
  }
}

Example: 401 Unauthorized

{
  "success": false,
  "error": {
    "code": "unauthorized",
    "fullCode": "RELM-GEN-UNAUTHORIZED",
    "msg": [
      "Invalid API key authentication"
    ],
    "source": "GEN",
    "statusCode": 401,
    "traceId": "63f10450-1bbb-11f1-ad67-93c03b26c699"
  }
}

Example: 404 Not Found

{
  "success": false,
  "error": {
    "code": "not-found",
    "fullCode": "RELM-GEN-NOT-FOUND",
    "msg": [
      "Currency USDE not found"
    ],
    "source": "GEN",
    "statusCode": 404,
    "traceId": "98c52fd0-1bbb-11f1-ad67-93c03b26c699"
  }
}

Demo

• Ecommerce store