SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2b6a6bb2531c8ff3293e585dac44e0289b9d855b5328726e98ff681d88188cdf' 
  AND token = '9XNZemvkuxrEcXxnJjjeWwsUm48igCrCfqUuma/3nak=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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