SELECT 
  variant_id, 
  yml2_unit 
FROM 
  cscart_product_feature_variant_descriptions 
WHERE 
  variant_id IN (
    '4796', '4793', '3953', '4766', '4803', 
    '4763', '4800', '4808', '4783', '4801', 
    '4787', '4773', '4799', '4779', '4776', 
    '4780', '4809', '4806', '4781', '4782', 
    '4784', '4789', '4797', '2051', '2933', 
    '1938', '3709', '2037', '1978', '2273', 
    '2375', '2613', '1858', '1862', '2349', 
    '1855', '1996', '5115', '1987', '1970', 
    '2711', '3748', '2004', '5137', '2499', 
    '1993', '3101', '3095', '1510', '1620', 
    '1297', '1143', '1777', '167', '1240', 
    '534', '1619', '113', '16', '63', '851', 
    '1618', '1269', '165', '1753', '878', 
    '1243', '3698', '1778', '169', '1851', 
    '3382', '221', '1381', '500', '1573', 
    '548', '1754', '1387', '222', '3378', 
    '391', '1793', '1436', '378', '2030', 
    '1870', '1859', 'Y', '1615'
  ) 
  AND lang_code = 'en'

Query time 0.00808

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_feature_variant_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["variant_id", "lang_code"],
          "rows": 90,
          "filtered": 100,
          "index_condition": "cscart_product_feature_variant_descriptions.variant_id in ('4796','4793','3953','4766','4803','4763','4800','4808','4783','4801','4787','4773','4799','4779','4776','4780','4809','4806','4781','4782','4784','4789','4797','2051','2933','1938','3709','2037','1978','2273','2375','2613','1858','1862','2349','1855','1996','5115','1987','1970','2711','3748','2004','5137','2499','1993','3101','3095','1510','1620','1297','1143','1777','167','1240','534','1619','113','16','63','851','1618','1269','165','1753','878','1243','3698','1778','169','1851','3382','221','1381','500','1573','548','1754','1387','222','3378','391','1793','1436','378','2030','1870','1859','Y','1615') and cscart_product_feature_variant_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}