Can Your Origin Server Survive the Moment You Clear the Cache?
A cache acts as a shield, absorbing most traffic so the origin server doesn't have to handle every request. But when a deploy or data update forces a full cache invalidation, every request the cache used to catch suddenly floods the origin all at once. If a system normally runs at a 90% cache hit ratio, clearing that cache can hit the origin with close to 10 times its usual load in an instant.
This calculator takes normal traffic (RPS), cache hit ratio, and origin server capacity, then calculates the load the origin has to absorb the moment the cache is invalidated, along with a multiplier against its capacity. A multiplier above 1 means the origin server is at serious risk of overload. Use it before a deploy to check your cache strategy, or to decide whether you need gradual invalidation or cache warming.
Frequently Asked Questions
All the requests the cache used to absorb suddenly hit the origin at once, so load jumps sharply within a short window.
Invalidate gradually instead of clearing everything at once, and combine that with cache warming and rate limiting.