SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fdc45daf30c13e9fbfb10dc6c597ffe262e83f5bf317f0751f8fedd4f416cc02' 
  AND token = '51+aCAclz1V4VnBqhxTI+HcmIUQqKKoPnNuOt58TSzc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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