Implement a banking operations system

Implement a simple banking system that manages multiple accounts with initial balances. Support operations: deposit(accountId, amount), withdraw(accountId, amount), and transfer(fromId, toId, amount). Reject operations that would overdraw an account or reference a non-existent account; for each operation return whether it succeeded. Provide a function that applies a sequence of operations and returns the final balances. Discuss data structures, edge cases (e.g., zero/negative amounts, large account counts), and time/space complexity. If operations arrive as a stream, explain how you would process them efficiently.