General Description

RESTful API to calculate statistics summary based on transaction data records received for the last 60 seconds. The solution works without a database (this also applies to in-memory databases).

API endpoints

POST /transactions

This endpoint is called every time a new transaction happened.

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

Where:

• amount: transaction amount; a string of arbitrary length that is parsable as a BigDecimal
• timestamp: transaction time in the ISO 8601 format YYYY-MM-DDThh:mm:ss.sssZ in the UTC timezone (this is not the current timestamp)

Returns: Empty body with one of the following:

201 – in case of success 204 – if the transaction is older than 60 seconds 400 – if the JSON is invalid 422 – if any of the fields are not parsable or the transaction date is in the future

GET /statistics

This endpoint returns the statistics computed on the transactions within the last 60 seconds.

Returns:

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

Where:

• sum: a BigDecimal specifying the total sum of transaction value in the last 60 seconds
• avg: a BigDecimal specifying the average amount of transaction value in the last 60 seconds
• max: a BigDecimal specifying single highest transaction value in the last 60 seconds
• min: a BigDecimal 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

All BigDecimal values always contain exactly two decimal places and use HALF_ROUND_UP rounding. eg: 10.345 is returned as 10.35, 10.8 is returned as 10.80

DELETE /transactions

This endpoint causes all existing transactions to be deleted

The endpoint should accept an empty request body and return a 204 status code.