SELECT 
  variant_id, 
  yml2_unit 
FROM 
  cscart_product_feature_variant_descriptions 
WHERE 
  variant_id IN (
    '1706', '1529', '1358', '1263', '1258', 
    '1345', '1355', '1299', '1251', '1320', 
    '1301', '1304', '1337', '1542', '8627', 
    '5893', '5891', '5888', '5889', '5890', 
    '1202', '5894', '5895', '5896', '5897', 
    '1541', '5898', '1230', '1449', '1201', 
    '1219', '5899', '1269', '1283', '5900', 
    '1281', '5901', '1255', '1257', '5902', 
    '5903', '5913', '5904', '5905', '5906', 
    '5907', '5908', '1282', '1425', '1313', 
    '1280', '1254', '5909', '1314', '1200', 
    '5910', '5912', '1198', '1203', '1199', 
    '5914', '1241', '5915', '5916', '5941', 
    '5940', '1204'
  ) 
  AND lang_code = 'kk'

Query time 0.00188

JSON explain

{
  "query_block": {
    "select_id": 1,
    "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": 67,
      "filtered": 100,
      "index_condition": "cscart_product_feature_variant_descriptions.variant_id in ('1706','1529','1358','1263','1258','1345','1355','1299','1251','1320','1301','1304','1337','1542','8627','5893','5891','5888','5889','5890','1202','5894','5895','5896','5897','1541','5898','1230','1449','1201','1219','5899','1269','1283','5900','1281','5901','1255','1257','5902','5903','5913','5904','5905','5906','5907','5908','1282','1425','1313','1280','1254','5909','1314','1200','5910','5912','1198','1203','1199','5914','1241','5915','5916','5941','5940','1204') and cscart_product_feature_variant_descriptions.lang_code = 'kk'"
    }
  }
}