Software Engineer · Online Assessment · Coding

Anthropic — Software Engineer ✅ Passed

Level: Senior-Level

Round: Online Assessment · Type: Coding · Difficulty: 6/10 · Duration: 60 min · Interviewer: Neutral

Topics: Object-Oriented Programming, Data Structures, Algorithms

Location: San Francisco Bay Area

Interview date: 2026-01-20

Summary

Round 1: Coding

Question: Design a simple banking system with account creation, deposits, and transfers, including timestamping.

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Details

Design a basic banking service that allows users to open accounts, deposit funds, and move money between accounts. Each request includes an integer timestamp, and all requests arrive in strictly increasing order of time, representing events in a real-time system.

Implement the BankingSystem class with the following methods:

BankingSystem() Initializes the system with no accounts.

boolean createAccount(int timestamp, String accountId) Creates a new account with the identifier accountId. The account should start with a balance of 0.

• Return true if the account is successfully created.
• Return false if an account with the same accountId already exists.

int deposit(int timestamp, String accountId, int amount) Adds the specified amount to the balance of the account identified by accountId.

• If the account exists, return the updated balance after the deposit.
• If the account does not exist, return -1.

int transfer(int timestamp, String sourceAccountId, String targetAccountId, int amount) Moves amount of money from sourceAccountId to targetAccountId.

• If the transfer completes successfully, return the new balance of the source account.

• Return -1 if any of the following conditions occur:

  • Either account cannot be found
  • The source and target account IDs are identical
  • The source account does not have enough balance to complete the transfer.

Solution ` from typing import List, Optional

class BankingSystem: def init(self, ): self.accounts = {} # Map to store account balances

def createAccount(self, timestamp: int, accountId: str) -> bool:
    if accountId in self.accounts:
        return False

    self.accounts[accountId] = 0
    return True

def deposit(self, timestamp: int, accountId: str, amount: int) -> int:
    if accountId not in self.accounts:
        return -1

    newBalance = self.accounts[accountId] + amount
    self.accounts[accountId] = newBalance
    return newBalance

def transfer(self, timestamp: int, sourceAccountId: str, targetAccountId: str, amount: int) -> int:
    # Check if both accounts exist and are not the same
    if (sourceAccountId not in self.accounts or targetAccountId not in self.accounts
            or sourceAccountId == targetAccountId):
        return -1

    # Check if the source account has enough balance
    sourceBalance = self.accounts[sourceAccountId]
    if sourceBalance < amount:
        return -1

    self.accounts[sourceAccountId] = sourceBalance - amount
    self.accounts[targetAccountId] = self.accounts[targetAccountId] + amount
    return self.accounts[sourceAccountId]

`