Capital One Interview (Full Virtual onsite) for Technical Lead Software Engineer

Round 1

Questions: Your task is to implement a simplified version of a banking system.

Initially, the banking system does not contain any accounts, so implement operations to allow accounts creation as well as making deposits.

Operations:

CREATE_ACCOUNT

Should create a new account with the given identifier if it doesn't already exist. Returns "true" if an account was successfully created, Returns "false" if an account with accountId already exists.

DEPOSIT

Should deposit the given amount of money to the specified account accountId Returns the total amount of money in the account after the query has been processed. If the specified account doesn’t exist, it should return -1.

TRANSFER

This should transfer the given amount of money from account with fromId to account with toId.

Returns the balance of fromId if the transfer was successful, or -1 otherwise. Returns -1 if fromId or toId doesn’t exist. Returns -1 if fromId and toId are the same. Returns -1 if funds on the account fromId are insufficient to perform the transfer.

TOP_ACTIVITY

This should return the identifiers of n most active accounts in descending order of financial activity indicator. In case of a tie, sorted alphabetically by accountId in ascending order.

The returned value should be an array of identifiers in the format <accountId_1>(<activity_indicator_1>), <accountId_2>(<activity_indicator_2>), ..., <accountId_n>(<activity_indicator_n>)

Financial activity indicator is defined as the sum of all transactions for an account including the money deposited and/or successfully transferred. Unsuccessful transactions are not included.

If less than n accounts exist in the system, then return all their identifiers (in the described format).

operations = [
  ["CREATE_ACCOUNT", "account1"],   # true
  ["CREATE_ACCOUNT", "account1"],   # false
  ["CREATE_ACCOUNT", "account2"],   # true
  ["DEPOSIT", "non-existing", "2700"],  # -1
  ["DEPOSIT", "account1", "2700"],  # 2700
  ["TRANSFER", "account1", "account2", "2701"],  # -1
  ["TRANSFER", "account1", "account2", "200"],  # 2500
  ["TRANSFER", "account1", "account2", "2500"], # 0
  ["DEPOSIT", "account2", "300"], #3000
  ["CREATE_ACCOUNT", "account3"], # true
  ["DEPOSIT", "account3", "4000"], #4000
  ["TOP_ACTIVITY", "3"],  #[account1(5400), account3(4000), account2(3000)]
  ["DEPOSIT", "account2", "1000"], # 4000
  ["TOP_ACTIVITY", "2"],  #[account1(5400), account2(4000)]
  ["TOP_ACTIVITY", "5"]  #[account1(5400), account2(4000), account3(4000)]
]

Round 2

Questions: Design a credit card account management application. The application should represent a bank with the opportunity to apply for credit cards, manage credit cards, manage payments, and report usages.

Features that need to be supported:

• Process a credit card application
• Create a credit card online account / access online portal
• Provide API to authorize credit card transactions
• Support calculating daily, weekly and monthly statistics
• Pay credit card balance using a third-party payment service

Round 3

Questions: The interviewer asked management-related questions, mistakenly thinking the candidate was interviewing for a managerial position.

Round 4

Questions: Asked about the quick replying model "Eeno" and suggestions for improvement.

Then asked to tweak the following code:

import calendar
import time

class RetrieverQ:
    def __init__(self, store):
        self.store = store

    def retrieve_recent(self, customer_id, curr_time):
        result = []
        # Retrieve data for the last 5 minutes including the current minute
        for index in range(0, 5):
            val = self.store.retrieve(customer_id, curr_time - 5 + index)
            if val is not None:
                result.append(val)
        return result

Questions Asked:

• Explain the code
• Given: cid = 1, curr_time = 25853655, What rows come back from the retrieve_recent function
• Modify the retrieve_recent function to retrieve a window of Time T minutes.

def retrieve_recent(self, customer_id, curr_time, time_window):  
    result = []
    for index in range(time_window):  # Use time_window directly in the loop
        val = self.store.retrieve(customer_id, curr_time - time_window + index + 1)
        if val is not None:
            result.append(val)
    return result