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 (
    69639, 69638, 69637, 69640, 70057, 70056, 
    70055, 70054, 70058, 70053, 70100, 
    70099, 70098, 70097, 70101, 70096, 
    70870, 70869, 70868, 70867, 70871, 
    70995, 70994, 70993, 70996, 71023, 
    71022, 71021, 71024, 71949, 73477, 
    73476, 73533, 73532, 73962, 73961, 
    73960, 73959, 73963, 77850, 77851, 
    77852, 80887, 80886, 80888, 80889, 
    81003, 81002, 81004, 81005, 81006, 
    81007, 85957, 85956, 85955, 85954, 
    85959, 85958, 84256, 84257, 84258, 
    84259, 85884, 85883, 87126, 87127, 
    87128, 87129
  )

Query time 0.00839

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": 68,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (69639,69638,69637,69640,70057,70056,70055,70054,70058,70053,70100,70099,70098,70097,70101,70096,70870,70869,70868,70867,70871,70995,70994,70993,70996,71023,71022,71021,71024,71949,73477,73476,73533,73532,73962,73961,73960,73959,73963,77850,77851,77852,80887,80886,80888,80889,81003,81002,81004,81005,81006,81007,85957,85956,85955,85954,85959,85958,84256,84257,84258,84259,85884,85883,87126,87127,87128,87129)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}