SELECT 
  cscart_products.*, 
  cscart_products.ebay_status, 
  cscart_products.ebay_template_id 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    20653, 20654, 20655, 20656, 20657, 20658, 
    20659, 20660, 20661, 20662, 20663, 
    20664, 20665, 20666, 20667, 20668
  )

Query time 0.00038

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 (20653,20654,20655,20656,20657,20658,20659,20660,20661,20662,20663,20664,20665,20666,20667,20668)"
    }
  }
}