A cold cache has no data. Every request is a cache miss, hammering the database.
Cache warming preloads data before traffic arrives.
Strategies:
- Run warm-up script at deploy time
- Replay recent access logs
- Copy from another cache instance
- Gradually shift traffic during warm-up
When to warm:
- After deployments
- After cache failures
- Before anticipated traffic spikes (product launch, Super Bowl)
Mention cache warming when discussing deployments or disaster recovery. It shows you think about operational details.