Surviving Flashes of High-Write Traffic Using Scriptable Load Balancers (Part I) - Shopify

What this post added

This post details the implementation of a scriptable load balancer using Nginx and Lua to handle extreme traffic spikes during flash sales. It addresses the challenges of checkout write traffic by implementing a leaky bucket algorithm and a cached queue page to maintain customer experience while protecting the platform. The solution was developed as a short-term measure to bridge the gap until a full refactor of the checkout flow could occur.