Transactions statistics N26

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

Commands

• Install - mvn clean install
• Run - mvn spring-boot:run
• Test - mvn integration-test

Author

Anton Kildishev anton_kildishev {at} mail.ru

API endpoints:

• POST /transactions – called every time a transaction is made. It is also the sole input of this rest API.
• GET /statistics – returns the statistic based of the transactions of the last 60 seconds.
• DELETE /transactions – deletes all transactions.

Specs:

POST /transactions

This endpoint is called to create a new transaction.

Body:

{ "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.