SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    21170, 21171, 21172, 21173, 21174, 21175, 
    21176, 21177, 21178, 21179, 21180, 
    21181, 21182, 21183, 21184, 21185, 
    21186, 21187, 21188, 21189, 21190, 
    21191, 21192, 21193
  )

Query time 0.00095

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_products",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "rows": 24,
          "filtered": 100,
          "index_condition": "cscart_products.product_id in (21170,21171,21172,21173,21174,21175,21176,21177,21178,21179,21180,21181,21182,21183,21184,21185,21186,21187,21188,21189,21190,21191,21192,21193)"
        }
      }
    ]
  }
}