How the 'Thundering Herd' problem can overwhelm your database despite caching

Adding a cache like Redis can reduce latency, but it does not automatically protect systems from the 'Thundering Herd' problem. This occurs when a large number of concurrent users — potentially hundreds of thousands — hit an empty or expired cache simultaneously. Instead of a single database query, the system receives an equal number of parallel queries, one from each user. The resulting surge can cause severe latency spikes, cascading failures, and even complete system downtime. Developers are being urged to account for this high-concurrency scenario when designing caching strategies.