nate.challenge.consumer

Technical challenge for Consumer Team engineering candidates

If you have any questions during the challenge you can drop an email to the developer/s that introduced the challenge to you.

Overview

nate is a universal shopping experience that is designed to purchase any online product on behalf of a user.

Challenges

The challenge is different for full-stack and backend candidates.

Before working on the challenge, please fork this repositoy. Add your solution to your fork.

Backend

• Create an endpoint in the API to purchase a product with a certain ID
  • Use lib/purchase-api.ts to execute a purchase
• Design a risk assessment flow that would execute after a product has been purchased (see src/risk.ts) with provided lib/risk-api.ts functions and lib/action-api.ts actions
  • Assume that more than 1 missed payment should reject the purchase
  • The balance should cover the cost of the product and reject otherwise
  • The risk score should be less than 80 to accept, above 90 to reject, and anything in-between should be flagged

General Notes

• The solution should include automated tests
• The code should be readable, well-factored, and easily testable

Full Stack

• Implement web app functionality to fetch product data from /products endpoint and display to the user
• Create a purchase product endpoint in the API
• Add some UI for products to execute a purchase using the new endpoint
• Refactor code & add some unit tests (web app & API)

Objects

A seamless purchase experience is a crucial part of our platform, and it involves a few important objects:

User: the person purchasing a product through nate

• userId (string): uniquely identifies a User
• Other data about a user (email, billing address, etc) can be ignored for this exercise

Product: an item that can be purchased at an online shop

• productId (string): uniquely identifies a Product
• productUrl (string): the URL that is used to access the product page on the web
• productPrice (number): the price of a product (it can be assumed that this includes any taxes or fees)
• discountCode (optional string): a code that can be used on checkout to apply a discount

Purchase: an entity representing a User buying a Product through nate

• purchaseId (string): uniquely identifies a Purchase
• paymentMethodId (string): a reference to a user's payment method they are using for the purchase
• status (success | merchant-rejected | charge-failed | invalid-details | pending | rejected): the status of a purchase in nate's systems
  • success: indicates that the product was purchased successfully for the user
  • merchant-rejected: indicates that the merchant rejected this purchase because of issues on their end
  • charge-failed: indicates that the payment method was rejected when checking out
  • invalid-details: indicates that the details for the purchase are invalid
  • pending: indicates that we have not yet started any process against the purchase
  • rejected: indicates that we have rejected the purchase and will not complete it

Risk Assessment

Sometimes, people behave in a fraudulent manner. There are lots of ways this can happen, and it's business-critical for nate to evaluate purchase risk before going through and buying something on behalf of a user.

When a risk assessment is performed, the possible outcomes are:

• accepted: the risk level is low enough to proceed with the purchase
• rejected: the risk level is too high for this purchase
• flagged_for_review: the risk level is uncertain, and this purchase should be reviewed manually

Project Layout

• api: server application that allows callers to interact with nate's systems
  • src: source code for the server
    • index.ts: the server entrypoint
    • risk.ts: source code for risk-related functionality
    • lib: external libraries & APIs that provide useful functionality for the business - note that these APIs are asynchronous and should not be modified
      • purchase-api.ts: an interface for executing a purchase
      • risk-api.ts: a collection of interfaces for providing risk-related data about a user or payment method
      • action-api.ts: a collection of interfaces for accepting, rejecting, or flagging a purchase after risk assessment