SELECT 
  cscart_products.*, 
  cscart_products.ebay_status, 
  cscart_products.ebay_template_id 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    19821, 19822, 19823, 19824, 19825, 19826, 
    19827, 19828, 19829, 19830, 19831, 
    19832, 19833, 19834, 19835, 19836
  )

Query time 0.00033

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 (19821,19822,19823,19824,19825,19826,19827,19828,19829,19830,19831,19832,19833,19834,19835,19836)"
    }
  }
}