Kqr Row Cache Contention Check Gets -

She hot-patched KQR’s logic to use :

KQR had a job: cache frequently accessed rows so the main disk could rest. For years, this worked beautifully. Until . kqr row cache contention check gets

def get(key): if key in cache: return cache[key] else: // Only one thread goes to DB; others wait for its result return cache.load_or_wait(key) Within 30 seconds, the contention ratio dropped from 1.00 to 0.001. She hot-patched KQR’s logic to use : KQR

From that day on, KQR’s monitoring dashboard had a new rule: If row cache contention check gets > 1000 per second — flip on single-flight mode. And the team learned a valuable lesson: sometimes, the most dangerous lock isn’t in your database — it’s in your cache’s eagerness to help . def get(key): if key in cache: return cache[key]

, the on-call engineer, saw the alert: kqr row cache contention check gets = CRITICAL She’d seen this before. It wasn’t a database problem — it was a thundering herd problem.