SELECT 
  cscart_products.*, 
  cscart_products.ebay_status, 
  cscart_products.ebay_template_id 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    20557, 20558, 20559, 20560, 20561, 20562, 
    20563, 20564, 20565, 20566, 20567, 
    20568, 20569, 20570, 20571, 20572
  )

Query time 0.00034

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 (20557,20558,20559,20560,20561,20562,20563,20564,20565,20566,20567,20568,20569,20570,20571,20572)"
    }
  }
}