SELECT 
  cscart_products.*, 
  cscart_products.ebay_status, 
  cscart_products.ebay_template_id 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    20477, 20478, 20479, 20480, 20481, 20482, 
    20483, 20484, 20485, 20486, 20487, 
    20488, 20489, 20490, 20491, 20492
  )

Query time 0.00031

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 (20477,20478,20479,20480,20481,20482,20483,20484,20485,20486,20487,20488,20489,20490,20491,20492)"
    }
  }
}