Under load the product-page cache expires all of its keys in the same second, so every request stampedes the database at once and the site falls over during traffic spikes — which is exactly what caused last week's outage. Adding jittered TTLs plus a single-flight lock, so only one request refills a cold key while the others wait, removes the thundering herd. @sam must land this before the Black Friday change freeze, otherwise we repeat the outage under peak traffic.
