SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19773, 19774, 19775, 19776, 19777, 19778, 
    19779, 19780, 19781, 19782, 19783, 
    19784, 19785, 19786, 19787, 19788
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00920

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 (19773,19774,19775,19776,19777,19778,19779,19780,19781,19782,19783,19784,19785,19786,19787,19788) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}