Design Product Catalogue with Real-Time Inventory Sync

Problem

Design Meesho's product catalogue and inventory system that serves millions of resellers and buyers simultaneously.

Requirements

Functional:

• Browse and search 10M+ SKUs
• Reseller sets custom price on catalogue products
• Real-time stock updates when orders are placed or cancelled
• Catalogue admin can add/update/remove products

Non-functional:

• 50M daily active users
• Search response < 200ms
• Inventory consistency: no oversell, eventual consistency on catalogue metadata acceptable

Discussion points

1. Catalogue service vs inventory service separation
2. Elasticsearch for search; Postgres for inventory
3. Write-ahead log tailing for inventory sync to search index
4. Caching strategy: what to cache, TTL, invalidation
5. Handling catalogue updates that affect thousands of reseller listings