Monitoring & Debugging a Checkout Flow in Flask & React

When a checkout flow breaks, customers disappear quickly. However, setting up observability with Sentry makes it painless to track user interactions and fix issues. By turning on Distributed Tracing in both frontend and backend applications, they captured performance metrics, errors, and tracing data. A dashboard was created to monitor the critical aspect of their eCommerce storefront: the checkout flow. The instrumentation allowed them to attach attributes to spans, such as the number of items added to a cart. This enabled them to spot issues like a complete dropoff in items added to carts, which they could drill into and see the root cause. They fixed a classic coding slip-up by initializing an empty array instead of None for product inventory. To improve their approach, they set alerts on span metrics and routed issues to the right team, making observability without context switching chaos possible with just a few lines of code.