Intermittent Homepage Outage: Root Cause Analysis

Challenge

The German-language homepage had been randomly going blank 2-3 times per week for several months. Cache clearing always restored it within minutes, so the team had been living with the problem rather than escalating it. The ask: find and permanently fix the root cause, not paper over it.

What Was Built

A monitoring script was deployed to catch the next failure in real time. Log analysis revealed suppressed PHP warnings and notices in both the custom CMS integration module and its counterpart on the CMS side, surfacing only under specific cache states after partial cache invalidation on the German storefront. All PHP warnings and errors in both modules were resolved (incorrect null checks, undefined array keys, type coercion edge cases). Cache layer logic was tightened: corrupt or empty cache entries now fall back gracefully instead of rendering a blank page. Monitoring script left running post-deploy for observation.