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 (
    71075, 71076, 81601, 81610, 81611, 81612, 
    81613, 81614, 81615, 81616, 81617, 
    81602, 81603, 81604, 81605, 81606, 
    81607, 81608, 81609, 83869, 83870, 
    84150, 84151, 84318, 84319, 84320, 
    84321, 85275, 85276, 85277, 85278, 
    85279, 87011, 87012, 87013
  )

Query time 0.00876

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": 35,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (71075,71076,81601,81610,81611,81612,81613,81614,81615,81616,81617,81602,81603,81604,81605,81606,81607,81608,81609,83869,83870,84150,84151,84318,84319,84320,84321,85275,85276,85277,85278,85279,87011,87012,87013)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}