SELECT 
  pfv.variant_id, 
  pfv.position, 
  pfvd.variant 
FROM 
  cscart_product_feature_variants AS pfv 
  INNER JOIN cscart_product_feature_variant_descriptions AS pfvd ON pfv.variant_id = pfvd.variant_id 
  AND pfvd.lang_code = 'vi' 
WHERE 
  pfv.variant_id IN (
    68977, 68976, 68975, 68978, 68974, 68994, 
    68993, 68992, 68991, 68990, 68989, 
    68988, 68987, 68995, 68986, 69030, 
    69029, 69028, 69027, 69026, 69025, 
    69024, 69023, 69031, 69022, 69038, 
    69037, 69036, 69035, 69034, 69033, 
    69039, 69032, 70010, 70009, 70008, 
    70011, 70007, 70028, 70027, 70026, 
    70025, 70024, 70029, 70033, 70032, 
    70031, 70030, 70034, 70057, 70056, 
    70055, 70054, 70058, 70053, 70088, 
    70089, 70087, 70100, 70099, 70098, 
    70097, 70101, 70096, 70991, 70992, 
    70995, 70994, 70993, 70996, 71005, 
    71004, 71003, 71002, 71001, 71006, 
    71013, 71012, 71011, 71014, 71015, 
    71016, 86606, 86607, 86608, 86851, 
    86852, 86853
  )

Query time 0.01026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["variant_id"],
          "rows": 88,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68977,68976,68975,68978,68974,68994,68993,68992,68991,68990,68989,68988,68987,68995,68986,69030,69029,69028,69027,69026,69025,69024,69023,69031,69022,69038,69037,69036,69035,69034,69033,69039,69032,70010,70009,70008,70011,70007,70028,70027,70026,70025,70024,70029,70033,70032,70031,70030,70034,70057,70056,70055,70054,70058,70053,70088,70089,70087,70100,70099,70098,70097,70101,70096,70991,70992,70995,70994,70993,70996,71005,71004,71003,71002,71001,71006,71013,71012,71011,71014,71015,71016,86606,86607,86608,86851,86852,86853)"
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["variant_id", "lang_code"],
          "ref": ["dev_db.pfv.variant_id", "const"],
          "rows": 1,
          "filtered": 100,
          "index_condition": "pfvd.lang_code = 'vi'"
        }
      }
    ]
  }
}