hesela.devDelayed cache hit
A delayed cache hit is a request for a nonresident object that joins an outstanding fetch and waits for its completion rather than initiating another fetch.
Not fetching again does not mean that data are ready. Separate resident hits, delayed hits and fetch-triggering misses when interpreting a cache metric. [1]
Hesela's constructed four-read example has one 10 ms fetch in every row. Arrivals at 0, 1, 2 and 3 ms produce waits of 10, 9, 8 and 7 ms, averaging 8.5 ms. Spacing arrivals to 0, 10, 20 and 30 ms instead gives 2.5 ms. Completion precedes equal-time arrivals; service after the fetch is instantaneous. These are model values, not device measurements. [2]