SELECT 
  cscart_products.*, 
  cscart_products.ebay_status, 
  cscart_products.ebay_template_id 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    20221, 20222, 20223, 20224, 20225, 20226, 
    20227, 20228, 20229, 20230, 20231, 
    20232, 20233, 20234, 20235, 20236
  )

Query time 0.00045

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": 16,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (20221,20222,20223,20224,20225,20226,20227,20228,20229,20230,20231,20232,20233,20234,20235,20236)"
    }
  }
}