SELECT 
  cscart_products.*, 
  cscart_products.ebay_status, 
  cscart_products.ebay_template_id 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    20029, 20030, 20031, 20032, 20033, 20034, 
    20035, 20036, 20037, 20038, 20039, 
    20040, 20041, 20042, 20043, 20044
  )

Query time 0.00043

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 (20029,20030,20031,20032,20033,20034,20035,20036,20037,20038,20039,20040,20041,20042,20043,20044)"
    }
  }
}