This is a lot to cover in one question and I didn't pace myself well.
Start by clarifying requirements and scope, then walk through the data model for timeslots and bookings, emphasizing concurrency control (e.g., optimistic locking or database constraints) to prevent double-booking. Next, explain the payment integration flow with idempotency keys and webhook handling, and finally describe the booking lifecycle state machine and failure/reconciliation strategies.
Pro tip: Emphasize idempotency and reconciliation as first-class concerns—show that you understand payments can fail or be delayed, and that the system must gracefully handle these cases without double-charging or double-booking.
Ask clarifying questions about expected traffic, payment provider, and whether real-time slot locking is needed. Define the core entities and user flow.
Propose a schema for providers, timeslots, and bookings. Explain how to prevent double-booking using database transactions, unique constraints, or optimistic locking.
Describe the payment flow: create a payment intent with an idempotency key, handle webhooks for asynchronous updates, and ensure idempotent processing of webhook events.
Outline states (e.g., pending, confirmed, cancelled, expired) and transitions triggered by user actions or payment events. Include timeouts for pending bookings.
Explain strategies for handling payment failures, webhook delays, and discrepancies between booking and payment states, such as periodic reconciliation jobs and manual intervention.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.