Preventing Database Stampedes with Single-Flight Caching Techniques

The article discusses the problem of cache stampedes, where multiple simultaneous requests for a cached resource trigger a surge in database queries, overwhelming the connection pool. This occurs when the cache expires under heavy load, causing redundant database calls. The solution presented is ‘single-flight caching,’ which ensures only one computation occurs for a given key, with subsequent requests waiting for the same result. This is implemented using an in-flight promise system that tracks ongoing computations. The approach maintains fast cache hits while preventing redundant queries. The text emphasizes that cache stampedes are not mitigated by larger pools or timeouts but by sharing computation across concurrent requests. The example highlights how this technique prevents database overload for a high-traffic key, reducing from 200 queries to a single database call. The article concludes that the key to avoiding stampedes lies in coordinating computations rather than relying solely on caching.