Architectureperformancecachingdebuggingprofiling
We Built a Cache That Made the System Slower
A team added Redis caching to speed up a slow API endpoint, but response times got worse.
Situation
You're a senior engineer at a SaaS company. The dashboard API endpoint takes 4 seconds under load, serving 50,000 transaction rows to compute metrics. Customer complaints are escalating, and your largest enterprise account is threatening to churn.
Stakes
- Key API endpoint serving the product's main dashboard was slow under load
- Customer complaints escalating — largest enterprise account threatened to churn
- Team spent 3 weeks building a caching layer that made the problem worse
Your tech lead proposes adding a Redis caching layer to cache database query results. It'll take about a week to implement. What's your first move?