What Is a Cache Miss?
A cache miss happens when a lookup finds no valid entry for the requested key, so the system must retrieve the value from the underlying source. The fetched value is typically stored in the cache so subsequent requests can hit. A miss costs the full origin latency plus the overhead of populating the cache.
Why it matters
Miss rate drives effective performance; frequent misses mean the cache is adding overhead without paying off. In CI, a missed dependency cache forces a full re-download, lengthening the job.
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