How would you make instant grocery substitution and availability reliable during peak demand under scale, incentive, and regulatory constraints?

Problem Statement Description

Blinkit customers often place grocery orders with an expectation of near-instant delivery, high item availability, and minimal back-and-forth during fulfillment. During peak demand windows—such as evenings, weekends, festivals, rain, or promotional surges—dark-store inventory can change rapidly, picker workload increases, and customers may receive late updates that an item is unavailable or needs substitution.

You are the Technical PM responsible for improving the reliability of instant grocery availability and substitution experiences for premium quick-commerce users. The challenge is to define how the product and systems should support accurate availability signals, fast substitution decisions, compliant handling of customer preferences, and dependable fulfillment without overloading store operations or delivery SLAs.

This is not only a customer-facing UX problem. It involves real-time inventory systems, picker apps, catalog and substitution logic, customer communication, pricing and incentive design, operational workflows, regulatory constraints around food, labeling, consent, and refunds, as well as observability at city, store, SKU, and order levels.

The experience should consider:

- How customers discover item availability before checkout and how confidence in availability is communicated without creating false promises.

- How substitution preferences, dietary restrictions, brand preferences, pack-size flexibility, allergies, and price sensitivity should be captured and respected.

- What APIs, data contracts, and event flows are needed across catalog, inventory, order management, picker app, customer app, payments/refunds, and delivery systems.

- How the system should behave during peak load when inventory signals are stale, pickers are constrained, or multiple customers are competing for the same SKU.

- How reliability, latency, consistency, and fallback behavior should be designed for real-time substitution and availability decisions.

- What privacy, consent, accessibility, and regulatory considerations apply when using customer preferences, food-related attributes, and automated recommendations.

- How incentives for pickers, stores, and customers could affect substitution quality, speed, abuse, and operational cost.

- What observability, alerts, audit trails, rollout controls, and guardrails are required to detect failures and maintain trust at scale.

Your goal is to frame the technical product approach, requirements, system boundaries, trade-offs, and rollout considerations for making grocery substitution and availability more reliable during high-demand periods, while protecting customer trust, fulfillment speed, operational efficiency, and regulatory compliance.