fraud-service's Introduction

Fraud service

The goal of this project is to build a solution for this problem statement from CloudWalk interview process.

Client

/client folder contains Python code for instantiating clients capable of sending requests with transactions to be validated.

/proto folder contains Protocol Buffers (gRPC) defining the communication channel between clients and servers.

/server folder contains Ruby code for a server capable of receiving requests with transactions to be validated.

Chargeback
- Like retrieving the same received value amount
- Rejects any transaction with parameter hasCbk with value true
Rate limiter
- Like too many requests from the same user
- Accepts at most:
  - 1 per second
  - 5 per minute
  - 50 per hour
  - 100 per day
- Which means, evaluate requests with same userId and reject potential frauds
Maybe to evaluate relation between:
- cardNumber and transactionAmount and userId
  - users don't have that many cards in general, guess less than 5 on average
  - any new card for an user, suspicious
  - unusual high amount for an user, suspicious
- transactionAmount and userId
  - unusual high amount for an user, suspicious
- transactionAmount and transactionDate and userId
  - unusual high value for an user at an odd day/time, suspicious
- deviceId and transactionAmount and userId
  - users don't have that many devices in general, guess less than 10 on average
  - any amount from a new device, suspicious
  - unusual high amount from a device, suspicious
- merchantId and transactionAmount and userId
  - unusual item for user, if high value and odd item, suspicious

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