SELECT 
  cscart_products.*, 
  cscart_products.ebay_status, 
  cscart_products.ebay_template_id 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    20141, 20142, 20143, 20144, 20145, 20146, 
    20147, 20148, 20149, 20150, 20151, 
    20152, 20153, 20154, 20155, 20156
  )

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 (20141,20142,20143,20144,20145,20146,20147,20148,20149,20150,20151,20152,20153,20154,20155,20156)"
    }
  }
}