in src/main/java/com/googlesource/gerrit/plugins/websession/broker/BrokerBasedWebSessionCache.java [187:192]
public void cleanUp() {
Instant now = timeMachine.now();
cache.asMap().entrySet().stream()
.filter(entry -> Instant.ofEpochMilli(entry.getValue().getExpiresAt()).isBefore(now))
.forEach(entry -> cache.invalidate(entry.getKey()));
}