Requirements: Adding a transaction and getting statistics must be executed in constant time and memory (O(1))
To start it up:
gradle run
To create a transaction (only transactions newer than 60 sec will be persisted):
curl 'http://localhost:9090/transactions' -XPOST -d '{"amount":300,"timestamp":1506979417000}' -H 'Content-Type: application/json'
(The timestamp can be generated with the date +%s000 command)
To get statistics from transactions in the last 60 seconds:
curl 'http://localhost:9090/statistics'