Start by clarifying requirements and edge cases, then outline a step-by-step algorithm that handles balance merging, scheduled transfer reassignment, spending history aggregation, and source account closure. Emphasize data consistency and atomicity, and discuss how you would test the implementation.
Pro tip: Mention the importance of atomicity and idempotency: if mergeAccounts is called twice or fails midway, the system should not be left in an inconsistent state. Also, consider how to handle scheduled transfers that reference the source account—they should be updated to point to the destination account.
Ask questions to understand constraints: Can accounts have negative balances? What happens to scheduled transfers if the source account is closed? Should historical spending be summed or kept separate? Are there any concurrency concerns?
Define the account structure (balance, scheduled transfers, spending history) and the merge operation. Consider using a transaction or lock to ensure atomicity. Outline how to update references from source to destination.
Write pseudocode: add source balance to destination, reassign scheduled transfers, combine spending totals, mark source as closed, and return new balance. Handle edge cases like merging into itself or merging closed accounts.
Discuss how to handle failures (e.g., rollback on error), prevent operations on closed accounts, and ensure that future operations on the source fail. Consider idempotency if the operation is retried.
Propose test cases: normal merge, merge with pending transfers, merge with spending history, merge into self, merge closed account, and concurrent merges. Verify that source account operations fail post-merge.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
This follow-up is where things got a bit uncomfortable.
Start by clarifying the business and regulatory constraints, then propose a hybrid policy: rewire transfers when the surviving account is valid and the transfer's intent is preserved, otherwise cancel with notification. Emphasize idempotent, transactional updates to all affected indexes and a reconciliation process to handle in-flight edge cases.
Pro tip: Mention that you would add a 'merge_id' to transfer records and use a two-phase commit or saga pattern to ensure atomicity across services, showing you understand distributed systems trade-offs.
Ask about business rules, regulatory requirements, and user expectations for transfers during account closure. Determine if transfers are user-initiated or system-scheduled and if they have external dependencies.
Propose criteria: rewire if the surviving account can fulfill the transfer and the user consents; cancel if the transfer is invalid or risky. Consider partial rewiring based on transfer type.
Use a distributed transaction or saga to update the transfer records and all related indexes (e.g., account balance, transfer status, audit logs) atomically. Ensure idempotency to handle retries.
For transfers already in progress, pause or queue them during merge, then apply the policy. Use a reconciliation job to detect and fix inconsistencies across indexes.
Log all decisions, notify affected users, and set up monitoring for failed rewires or cancellations. Provide an audit trail for compliance.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.