• Install HTTPie, on a mac you install with the below command.

$ brew install httpie

• Modify /etc/hosts file

$ sudo vim /etc/hosts
// enter your password

• Add the line

127.0.0.1      platform

• Propagate the changes:

$ sudo killall -HUP mDNSResponder

• Clone this repository and start the services

$ git clone https://github.com/tabotkevin/gr4vy-platform-challenge.git
$ cd gr4vy-platform-challenge
$ git fetch
$ git checkout answer
$ docker-compose up

• In another terminal, send a request to the http://platform/auth/token with one of the username and password combinatioins in auth-api/users.json

$ http post http://platform/auth/token username=alice password=password

• Expect a response like this

HTTP/1.1 200
Connection: keep-alive
Content-Length: 179
Content-Type: application/json
Date: Fri, 29 Apr 2022 02:05:39 GMT
Server: nginx/1.21.6

{
    "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyX2lkIjoxLCJ1c2VybmFtZSI6ImFsaWNlIiwiZW5hYmxlZCI6dHJ1ZSwiZXhwIjoxNjUxMTk3OTY5fQ.ZzlsWB7QpN636exFRxJZoQjzSmBrtwozHSixVigiQ70"
}

• Use the above token make the next request to http://platform/transaction

$ http post http://platform/transaction token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyX2lkIjoxLCJ1c2VybmFtZSI6ImFsaWNlIiwiZW5hYmxlZCI6dHJ1ZSwiZXhwIjoxNjUxMTk3OTY5fQ.ZzlsWB7QpN636exFRxJZoQjzSmBrtwozHSixVigiQ70 user_id=1 amount=100 currency=EUR

• Expect a response like this

HTTP/1.1 200 OK
Connection: keep-alive
Content-Length: 44
Content-Type: application/json
Date: Fri, 29 Apr 2022 02:05:45 GMT
Server: nginx/1.21.6

{
    "amount": 100,
    "currency": "EUR",
    "user_id": 1
}

Gr4vy is a building a payment orchestration platform.

As a Platform engineer, you are tasked with improving the engineering efficiency by producing automation tools that provision services in an efficient, predictable and reproducible way.

In this exercise we use HTTPie in our examples for clarity.

+----------------------------------+
|            Merchant              |
+-+--------^------------+--------^-+
  |        |            |        |
 (1)      (2)          (3)      (5)
  |        |            |        |
+-v--------+-+        +-v--------+-+        +-----------------+
|  Auth API  |        |  Core API  |        |  PSP Connector  | 
+------------+        +------+-----+        +---------^-------+
                             |                        |
                            (4)                      (6)
                             |                        |
                      +------v------------------------+-------+
                      |          Redis Message Queue          |
                      +---------------------------------------+

There are 3 distinct services:

• Auth API - Creates authentication tokens to valid users.
• Core API - Processes transaction requests.
• PSP Connector - Processes the transactions with a Payment Service Provider (PSP).

A transaction flow is as follows:

1. A merchant authenticates with the Auth API by providing a valid username and password.
2. An authentication token that is valid for 30 seconds is returned.
3. Use this authentication token to make a transaction request to the Core API.
4. The Core API submits the transaction to a message queue for further background processing.
5. A successful response is returned.
6. Meanwhile, a PSP Connector processes the transaction from the message queue by connecting to a Payment Service Provider.

We use environment variables to configure a service.

• Read the documentation for each service. Run and test them to make sure they work as expected.
• Once you're familiar with the services, use your preferred tools to automate provisioning of a local development environment.
• Be sure to include external dependencies like Redis and configuration management.
• In order for a microservices-based architecture to work best, implement a HTTP router in front of the services that routes requests to the correct service. A popular solution is path-based routing:
  • http://platform/auth/* → http://auth-api/*
  • http://platform/transaction/* → http://core-api/*
• Make your automation available on a public GitHub repository with a README on how to get things started.

Don't worry too much about making this production ready. We may discuss production considerations with you later on.

Please spend no more than 1-2 hours on this exercise.

• Containerise services.
• Apply the Twelve Factor App methodology.