SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '319d79048d2f349d1b96a17104341b442e5d37e9b3cecc749328ae35b62809f8' 
  AND token = 'WZLg6hfjw+29cJp+UJpYhMZYmU03mVHtYAhpgswxQYU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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