# FazzFinancial Platform Engineering Interview Questions

## 1. Deposit & Withdrawal

Given the following Ruby on Rails program, talk about:

class TransactionController < ActionController::Base
    def deposit
        TransactionJob.perform_later(
            account_id: params[:account_id],
            amount: BigDecimal(params[:amount]),
        )
        render json: {"ok" => true}
    end
    
    def withdrawal
        TransactionJob.perform_later(
            account_id: params[:account_id],
            amount: BigDecimal(params[:amount]) * -1,
        )
        render json: {"ok" => true}
    end
end

class TransactionJob < ActiveJob::Base
    def perform(account_id:, amount:)
        account = Account.find(account_id)
        if account.balance + amount >= 0
            account.balance += amount
            account.save
        end
    end
end

# CREATE TABLE `accounts` (
#   `id` INT,
#   `balance` DECIMAL
# );
class Account < ActiveRecord::Base
end

### performance issues

TODO

### concurrency issues

TODO

### user experience issues

TODO

## 2. Distributed Transaction

> A distributed transaction is a set of operations on data that is performed across two or more databases.

Create a microservice supporting distributed transaction and the following operations:

1. deposit(account_id:, amount:)
2. withdrawal(account_id:, amount:)
3. transfer(sender_account_id:, recipient_account_id:, amount:)

Please consider the following topics:

### the tools you would use to create such service

TODO

### performance & user experience

TODO

### maintainability

TODO

### development time estimation

TODO