SELECT 
  cscart_products.*, 
  cscart_products.ebay_status, 
  cscart_products.ebay_template_id 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    18669, 18670, 18671, 18672, 18673, 18674, 
    18675, 18676, 18677, 18678, 18679, 
    18680, 18681, 18682, 18683, 18684
  )

Query time 0.00048

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 (18669,18670,18671,18672,18673,18674,18675,18676,18677,18678,18679,18680,18681,18682,18683,18684)"
    }
  }
}