SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3b16c642859b96bbae91991206a28755ecb3ff260107ac688d175f1f05755919' 
  AND token = 'yIiO6HbHCB0X1us0DdtgSh8rV9avODg3uUfWRYCSo0c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}