Deadlock-Free Account Transfers | Dataford Interview Questions

Create a thread-safe account service that handles deposits, withdrawals, and bank transfers between accounts while avoiding deadlocks at Revolut.

Implement process_operations(initial_balances, operations, workers). Each operation is a dictionary describing a deposit, withdrawal, or transfer. Execute operations concurrently and return results in input order together with final balances. Deposits and withdrawals lock one account; transfers must acquire two account locks in a consistent global order. A withdrawal or transfer fails without changing balances when funds are insufficient.

Input amounts are positive integers and all referenced accounts exist.

Constraints

1 <= len(initial_balances) <= 10^4
1 <= len(operations) <= 10^4
0 < workers <= 64
All account identifiers referenced by operations exist in initial_balances
All amounts are positive integers
Initial balances are non-negative integers

Function Signature

def process_operations(initial_balances, operations, workers):

Your question is Deadlock-Free Account Transfers. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Create a thread-safe account service that handles deposits, withdrawals, and bank transfers between accounts while avoiding deadlocks at Revolut.

Input amounts are positive integers and all referenced accounts exist.

Constraints

1 <= len(initial_balances) <= 10^4
1 <= len(operations) <= 10^4
0 < workers <= 64
All account identifiers referenced by operations exist in initial_balances
All amounts are positive integers
Initial balances are non-negative integers

Function Signature

def process_operations(initial_balances, operations, workers):

Your question is Deadlock-Free Account Transfers. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.