SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '998d97e46441ab5278a847b95893cc75372da44f88bffb5192dc9268bdb47966' 
  AND token = 'u+dYMbNagJ1NAD5RxSwDzfRTCLEFC547H5fS5EYmlEU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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