SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19613, 19614, 19615, 19616, 19617, 19618, 
    19619, 19620, 19621, 19622, 19623, 
    19624, 19625, 19626, 19627, 19628
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00302

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id", "idx_product_lang"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (19613,19614,19615,19616,19617,19618,19619,19620,19621,19622,19623,19624,19625,19626,19627,19628) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}