PROJECT

Building a High-Performance, Event-Driven Cart Experience for Peak Sales

Re-architected our cart as an event-driven system to survive Black Friday peaks with flawless data.

Building a High-Performance, Event-Driven Cart Experience for Peak Sales screenshot

Overview

During holiday peaks, the old cart froze under concurrent price/promos updates—customers saw stale info and conversions plummeted.

Challenges

  • Preventing cart freezes under 10× normal traffic
  • Serving real-time stock & promo data without stale counts
  • Maintaining accurate pricing during rapid promo changes

Solutions

  • Switched to event-driven WebSocket broadcasts for stock, price, and promo events
  • Batched updates with Shopify’s GraphQL Bulk API (100 items per call)
  • Added a personalization layer to suggest upsells in-cart based on user behavior
  • Built an AWS Lambda + SQS fan-out pipeline to auto-scale cart events

Screenshots

Building a High-Performance, Event-Driven Cart Experience for Peak Sales screenshot 1
Building a High-Performance, Event-Driven Cart Experience for Peak Sales screenshot 2
Building a High-Performance, Event-Driven Cart Experience for Peak Sales screenshot 3

Final Notes

This solidified my event-driven architecture skills and boosted conversions in the process.
  • Cart load time ↓ 40% under peak
  • Handled 10× baseline traffic with zero manual ops
  • Conversion rate ↑ 18% during high-demand events
  • Promo accuracy ↑ 100%, eliminating disputes

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