Yellow Card Backend Engineering Test

Summary

This project contains the basic skeleton for a simple local serverless service. This environment contains an API endpoint, a dynamodb table, and a seed. The example endpoint scans the table for transactions and returns as many as it can. DynamoDB has a 1MB limit on the amount of data it will retrieve in a single request.

The goal is to create an endpoint to fetch transactions of specific currency on a certain country. Make sure pagination is supported such that a Client could specify the size of the transctions to retrieve, and the page (or other identifier). The transactions must be sorted by time with the most recently created as the first transaction.

Data

Supplied is a pre-generated list of transactions that will be seeded upon database start (txs.json). The generation script (tx-init.js) is also included and can be modified to include extra data if neccessary to achieve results.

Example transaction feature currency and country

{
    "id":"0",
    "amount":793.93,
    "country":"BW",
    "createdAt":1606186591726,
    "updatedAt":1606186591726,
    "currency":"USDT",
    "bitcoinAddress":"19xiZnXJexGgC6R1Tp9M8L7P8MsRhCE5",
    "customerName":"Jenny Kunze",
    "customerEmail":"Lavonne.Oberbrunner@yahoo.com",
    "customerId":"Kayla_Hilll"
}

Setup

1. Install Serverless Framework:

   npm i -g serverless
   

2. Install local modules

   npm i
   

3. Install local Dynamodb Instance

   serverless dynamodb install
   

4. Start local service

   sls offline start
   

5. Install Dynamodb-admin for AWS-like table explorer (optional)

Problem

DynamoDb actions limit to 1mb of data per call. This table has 30,000 transactions and can only retrieve ~5,286 of them.

The API Endpoint must accept country code, currency, the size limit of the # of transactions to retrieve per page, and some identifier, whether it be a page number or unique key, to be able to traverse forwards and backwards in the results in order.

Notes

Remember, the end result is an API that is setup for a transaction history page on a UI. There is far from a single solution. This problem is open-ended such that attributes can be added to the generated data, indexes can be added on the resource configuration in serverless.yml, etc.

Performance and elegance is important. Scans do not have to be used.

Review

We've set this project up in a way that allows for a simple review process from start to finish.

1. Clone this repository to your local machine
2. Create a new private repository for yourself called yellowcard-engineering-test
3. Follow the instructions to push an existing repository to push this project to your new private repository
4. Add @uncle-scooter and @okolilemuel as collaborators to your new private repository