SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19437, 19438, 19439, 19440, 19441, 19442, 
    19443, 19444, 19445, 19446, 19447, 
    19448, 19449, 19450, 19451, 19452
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.01049

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 (19437,19438,19439,19440,19441,19442,19443,19444,19445,19446,19447,19448,19449,19450,19451,19452) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}