🚨 Redis Mistake That Broke My Production System (Eviction Policy Lesson)

Jayhind Indian — Sun, 12 Apr 2026 17:28:24 +0000

Recently, I ran into a production issue that looked small at first… but ended up impacting a critical feature.

This is something many developers overlook when using Redis.

🧠 The Setup

I was using Redis for:

Everything was working perfectly in the beginning.

❌ The Problem

I did NOT configure any eviction policy.

As traffic increased:

The worst part?
There was no obvious error initially — things just started behaving incorrectly.

🔍 Root Cause

By default, if Redis reaches its memory limit ("maxmemory") and no proper eviction policy is configured:

👉 Redis starts rejecting new write operations.

This caused:

🛠️ The Fix

I updated Redis configuration:

maxmemory 256mb
maxmemory-policy allkeys-lru

Why "allkeys-lru"?

📈 Result

After applying the fix:

💡 Key Learnings

If you're using Redis in production:

✅ Always do this:

📌 Choose wisely:

🔥 Final Thought

Never rely on default configurations for production systems.

Small misconfigurations in infrastructure can break entire systems silently.

🙌 Closing

This was a small mistake, but a big learning.

If you're building scalable backend systems, Redis configuration is just as important as your application logic.

redis #backend #nodejs #systemdesign #learninginpublic