Transactions

A RESTful API for transactions statistics. Its main use case is to calculate realtime statistics for the last 60 seconds of transactions.

Implementation of a interview process coding challenge. You can look at the original question here.

Structure

• main.go: Main entrypoint, configurations stuff.
• middleware.go: Middleware for logging purposes.
• router.go: Defines two routers for the avaliable endpoints. Redirects to the handlers.
• handlers.go: The handlers for every REST resource.
• models.go: The general models and constants definitions. No methods nor functions here.
• transactions.go: The transactions models methods and functions.
• statistics.go: The statistics models methods and functions.
• app.go: The app model methods and functions. The main DB logic resides here.
• utils.go: Utilities and stuff used in other files. Has a test file.
• Makefile: The Makefile xd.

To run

Just run make. To run the tests make test.

API

/transactions

GET

Get the transactions db.

Example response

[
  {
    "amount": 88,
    "timestamp": "2020-09-25T20:05:48.539Z"
  },
  {
    "amount": 27,
    "timestamp": "2020-09-25T20:05:49.100Z"
  }
]

Return codes

• 201: If OK.
• 500: If something weird happened.

POST

Called every time a transaction is made. It is also the sole input of this rest API.

Parameters

Passed in the request body (JSON)

• amount: Arbitrary BigDecimal.
• timestamp: ISO 8601 timestamp.

Example request body

{
    "amount": "12.3343",
    "timestamp": "2018-07-17T09:59:51.312Z"
}

Return codes

• 201: If OK.
• 204: If transaction older than 60 seconds
• 400: JSON is invalid
• 422: Field/s not parsable or future transaction

DELETE

Deletes all transactions.

Returns

• 204: If OK , it may also return the number of transactions deleted, for example.

/statistics

GET

Returns the statistic based of the transactions of the last 60 seconds.

Return parameters

• sum: decimal specifying the total sum of transaction value in the last 60 seconds
• avg: decimal specifying the average amount of transaction value in the last 60 seconds
• max: decimal specifying single highest transaction value in the last 60 seconds
• min: decimal specifying single lowest transaction value in the last 60 seconds
• count: a long specifying the total number of transactions that happened in the last 60 seconds

Example response

{
    "sum": "1000.00",
    "avg": "100.53",
    "max": "200000.49",
    "min": "50.23",
    "count": 10
}

Returns

• 201: If OK.