SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b75d150e2e1fd7ecef70c21037b2fb06a210d863ca0a075d1954e3556cbe454' 
  AND token = 'Kdb4QjhAaXhHvALWtfbaDGjXAwj0wlKzXQ0T8wUPiOM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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