SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    421856, 453293, 421836, 444708, 429476, 
    413127, 407471, 409966, 403355, 408795, 
    420652, 443583
  )

Query time 0.00063

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.0216566,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_products",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "loops": 1,
          "rows": 12,
          "cost": 0.0216566,
          "filtered": 100,
          "attached_condition": "cscart_products.product_id in (421856,453293,421836,444708,429476,413127,407471,409966,403355,408795,420652,443583)"
        }
      }
    ]
  }
}