AI & Technical question

Design a ledger for a payment processing system.

Practice this question out loud. An AI interviewer asks it, follows up like a real interviewer would, and scores your answer. Type or speak.

What this question tests

Tests technical and financial systems design where correctness and auditability matter more than speed.

Clarify scope: internal balance movements via double-entry ledger, or transaction logs, with the interviewer.
Choose the core model: double-entry bookkeeping, every transaction debits one account and credits another.
Design for immutability: append-only entries, corrections via new offsetting entries, preserving a full audit trail.
Address consistency: a single source of truth with strict transactional guarantees, since partial writes corrupt balances.
Address scale: periodic read-optimized balance snapshots from the append-only log, avoiding full recomputation.
Define success as zero unbalanced entries and full reconciliation accuracy during periodic audits.

Chooses double-entry bookkeeping specifically, the standard model, not a generic 'database of transactions.'
Makes the ledger append-only and immutable, reflecting how real financial systems maintain auditability.
Names balance consistency as the concrete correctness metric, the real bar for a ledger system.

Designing a mutable transaction table where records can be edited or deleted.
No mention of consistency guarantees, risking corrupted balances under concurrent writes.

Chapters of the AI PM course that teach what this question tests.