Hot keys
On This Lesson 4 topics
This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.
In this lesson
detect and mitigate a key that takes a disproportionate share of traffic.
Planned topics
- A hot key: one product during a flash sale. A Redis node (or one instance) serving it becomes the bottleneck.
- Detect: per-key access counts,
redis-cli --hotkeys(needs an LFU policy; verify), or metrics from the client. - Mitigate: local L1 cache with short TTL in each instance, replicate the key under several names (
product:7#1..#4) and read at random, or serve through CDN. - Combine with stampede protection: a hot key expiring is the worst case.
Draft outline details
Demonstration
read path: Caffeine (2 s TTL) → Redis → database, so 20 instances send at most 10 requests per 20 s to Redis for that key.
Check your understanding
How does a short-lived local cache help with a hot key?
Show answer
Most reads never reach Redis.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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