Remote Decisioning Mock

A reference implementation of a customer remote authorization / decisioning endpoint for the PEX platform, built as an Azure Functions app (.NET 10 isolated worker).

When customer decisioning is enabled, PEX calls your endpoint in real time for each card transaction; your service approves or declines it. This repo is a minimal, runnable example of that endpoint — use it to understand the request/response contract and as a starting point for your own implementation.

The decision rules here are illustrative only (e.g. "approve when the amount is even"). They exist to make each scenario easy to trigger in testing. Replace them with your own authorization logic.

For the authoritative contract, see the PEX developer docs: https://developer.pexcard.com/documentation

The contract

PEX sends an HTTP POST with a DecisionRequest JSON body. Your endpoint returns a DecisionResponse:

• Approve → HTTP 200 with "Decision": 2
• Decline → HTTP 400 with "Decision": 0

// Approve
{ "NetworkTransactionId": 123, "Decision": 2, "Note": "approved" }
// Decline
{ "NetworkTransactionId": 123, "Decision": 0, "Note": "declined" }

JSON property names are PascalCase (see Program.cs, which configures the serializer accordingly). The Decision values (Approved = 2, Declined = 0) are defined by the contract.

Endpoints

This sample exposes several endpoints, each isolating one decision input so a scenario is easy to reproduce. A real service would expose a single decisioning endpoint.

Route	Illustrative behavior
decision/Authorization, decision/Authorization2	Approve when TransactionAmount is an even whole number
decision/PsiAuthorization	Approve when MCCCode == "5047" and TransactionAmount <= 5000
decision/authorizationtest/international	Approve when IsInternational is true
decision/authorizationtest/cardpresence	Decline when IsCardNotPresent is true
decision/authorizationtest/mcccategory	Approve when MCCCode == "3052"
decision/authorizationtest/timeout	Wait 2.5s then approve (exercises caller timeout handling)

It also implements the optional reachability check:

Route	Behavior
GET /Ping	Returns 200 with { "ResponseDateTime": <UTC ISO 8601> }. PEX uses this to monitor reachability (target < 500ms).

Authenticating requests

This sample uses anonymous endpoints for simplicity. In production, PEX can send a shared secret as an HTTP Basic Authorization header (configured per card program). Your endpoint should validate that header and reject unauthorized calls — add that check at the start of each function before processing the request.

Build & run locally

Requires the Azure Functions Core Tools and the .NET 10 SDK.

dotnet build DecisionEngine.Remote.Simulator.sln -c Release

cd DecisionEngine.Simulator/DecisionEngine.Remote.Simulator.Function
func start

Then call an endpoint, e.g.:

curl -i -X POST http://localhost:7071/api/decision/Authorization \
  -H "Content-Type: application/json" \
  -d '{"NetworkTransactionId":1,"TransactionAmount":2}'

local.settings.json ships with safe local defaults (AzureWebJobsStorage=UseDevelopmentStorage=true). Provide a real storage connection string when deploying.

Projects

Project	Purpose
DecisionEngine.Remote.Simulator.Common	Request/response models (DecisionRequest, DecisionResponse, DecisionEnum, PingResponse)
DecisionEngine.Remote.Simulator.Function	HTTP-triggered functions implementing the example endpoints

License

MIT — see LICENSE.