SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    20249, 20250, 20252, 20248, 20251, 20243, 
    20245, 20244, 20247, 20246, 20262, 
    20263, 20264, 20235, 20260, 20259, 
    20261, 20331, 20333, 20335, 20332, 
    20391, 20334, 20390
  )

Query time 0.00103

JSON explain

{
  "query_block": {
    "select_id": 1,
    "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 (20249,20250,20252,20248,20251,20243,20245,20244,20247,20246,20262,20263,20264,20235,20260,20259,20261,20331,20333,20335,20332,20391,20334,20390)"
    }
  }
}