Design a product catalog service for an e‑commerce site. Requirements: support hierarchical categories using a self‑referential Category table; products can belong to multiple categories; model product variants (size/color) and attributes; expose APIs to create/update products and categories, browse by category, search/filter by attributes, and fetch product detail. Specify a relational schema (tables, key fields, indexes) with the self‑join for categories, example API endpoints with request/response, pagination, and filtering. Discuss consistency choices, caching, read/write patterns, and how you would scale to 10M products and 1k QPS reads.

This question evaluates system design skills including relational data modeling, hierarchical category representation, product variant and attribute modeling, API design, caching, and search/index consistency trade-offs for an e-commerce product catalog.

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This is a medium difficulty System Design question, commonly asked during Onsite rounds at Instacart.

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Design an e-commerce catalog | Instacart Interview Question

System Design: Product Catalog Service

You are designing a product catalog service for an e‑commerce site. Assume a read‑heavy workload, a relational primary store, and JSON over HTTP APIs.

Requirements:

Data model
- Hierarchical categories using a self‑referential Category table (parent → child). Show the self‑join for categories.
- Products can belong to multiple categories.
- Model product variants (e.g., size/color) and arbitrary attributes.
- Specify a relational schema: tables, key fields, and indexes.
APIs
- Create/update products and categories.
- Browse products by category with pagination and filtering.
- Search/filter by attributes.
- Fetch product detail.
- Provide example endpoints with example request/response payloads. Include pagination and filtering syntax.
Architecture/operations
- Discuss consistency choices (DB vs. cache vs. search index), caching, read/write patterns.
- How to scale to 10M products and ~1k QPS reads.

Assumptions (you may refine): JSON APIs, REST style; prices/inventory may be separate services; 10M products, typical product has a few variants; peak read 1k QPS, writes much lower.

System Design: Product Catalog Service

You are designing a product catalog service for an e‑commerce site. Assume a read‑heavy workload, a relational primary store, and JSON over HTTP APIs.

Requirements:

Data model

Hierarchical categories using a self‑referential Category table (parent → child). Show the self‑join for categories.
Products can belong to multiple categories.
Model product variants (e.g., size/color) and arbitrary attributes.
Specify a relational schema: tables, key fields, and indexes.

APIs

Create/update products and categories.
Browse products by category with pagination and filtering.
Search/filter by attributes.
Fetch product detail.
Provide example endpoints with example request/response payloads. Include pagination and filtering syntax.

Architecture/operations

Discuss consistency choices (DB vs. cache vs. search index), caching, read/write patterns.
How to scale to 10M products and ~1k QPS reads.

Assumptions (you may refine): JSON APIs, REST style; prices/inventory may be separate services; 10M products, typical product has a few variants; peak read 1k QPS, writes much lower.

Design an e-commerce catalog

Quick Overview

System Design: Product Catalog Service

Solution

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Design an e-commerce catalog

Quick Overview

System Design: Product Catalog Service

Solution

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