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Client and Loan Management System

Objective

The main objective of this project is to create an API to manage clients and the loan payments control system from a fin-tech.

Purpose

The purpose of this challenge is to test your ability to implement a solution given an abstract problem. You may find a problem in the asked task that you need to explain the problem and propose a solution to fix it.

Problem

A fin-tech needs to create and manage the clients and keep track of the amount of money loaned and the missed/made payments. It also needs a place to retrieve the volume of outstanding debt at some point in time.

Business Rules

  • If a client contracted a loan in the past and paid all without missing any payment, you can decrease by 0.02% his tax rate.
  • If a client contracted a loan in the past and paid all but missed until 3 monthly payments, you can increase by 0.04% his tax rate.
  • If a client contracted a loan in the past and paid all but missed more than 3 monthly payments or didn’t pay all the loan, you need to deny the new one.

Limitations

Loans are paid back in monthly instalments.

Endpoints

POST /clients

Summary

Create a client in the system.

Payload

  • name: the client name.
  • surname: the client surname.
  • email: the client email.
  • telephone: the client telephone.
  • cpf: the client (Cadastro de Pessoa Física) identification.

Example of sent data

{
    "name": "Felicity",
    "surname": "Jones",
    "email": "felicity@gmail.com",
    "telephone": "11984345678",
    "cpf": "34598712387"
}

Reply

  • client_id: unique id of a client.

Example of received data

{
    "client_id": 1
}

POST /loans

Summary

Create a loan application. Loans are automatically accepted.

Payload

  • client_id: the client's identification that contracted a loan.
  • amount: loan amount in dollars.
  • term: number of months that will take until the loan gets paid-off.
  • rate: interest rate as decimal.
  • date: when the loan was requested (origination date as an ISO 8601 string).

Example of sent data

{
    "client_id": 1,
    "amount": 1000,
    "term": 12,
    "rate": 0.05,
    "date": "2019-05-09 03:18Z"
}

Reply

  • loan_id: unique id of the loan.
  • instalment: monthly loan payment.

Example of received data

{
    "loan_id": "000-0000-0000-0000",
    "instalment": 85.60
}

Notes

Loan payment formula

r = rate / term
instalment = [r + r / ((1 + r) ^ term - 1)] x amount

Example

For repaying a loan of $1000 at 5% interest for 12 months, the equation would be:

instalment = [(0.05 / 12) + (0.05 / 12) / ((1 + (0.05 / 12)) ^ 12 - 1] x 1000
instalment = 85.60

POST /loans/<:id>/payments

Summary

Create a record of a payment made or missed.

Payload

  • payment: type of payment: made or missed.
  • date: payment date.
  • amount: amount of the payment made or missed in dollars.

Example of sent data (Payment made)

{
    "payment": "made",
    "date": "2019-05-07 04:18Z",
    "amount": 85.60
}

Example of sent data (Payment missed)

{
    "payment": "missed",
    "date":  "2019-05-07 04:18Z",
    "amount": 85.60
}

POST /loans/<:id>/balance

Summary

Get the volume of outstanding debt (i.e., debt yet to be paid) at some point in time.

Payload

  • date: loan balance until this date.

Example of sent data

{
    "date": "2017-09-05 02:18Z"
}

Reply

  • balance: outstanding debt of loan.

Example

{
    "balance": 40
}