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 (
    68602, 68603, 68680, 68679, 70239, 70238, 
    70237, 70236, 70235, 70234, 70249, 
    70248, 70247, 70246, 70245, 70244, 
    70243, 70242, 70241, 71341, 71339, 
    71338, 71337, 71336, 71335, 71334, 
    71333, 71332, 71331, 71342, 74799, 
    74800, 74803, 74804, 75515, 75516, 
    75520, 75519, 76705, 76704, 76703, 
    76706, 80475, 80474, 80476, 80477, 
    81655, 81656, 81657, 81658, 81659, 
    81660, 81661, 81662, 81689, 81690, 
    81691, 86592, 86593, 86594, 86595, 
    87021, 87022, 87023, 87098, 87097, 
    87096, 87094, 87095, 84152, 87604, 
    84154, 87603, 87602, 87601, 84156, 
    84153, 87711, 87712, 87713
  )

Query time 0.00708

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": 80,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68602,68603,68680,68679,70239,70238,70237,70236,70235,70234,70249,70248,70247,70246,70245,70244,70243,70242,70241,71341,71339,71338,71337,71336,71335,71334,71333,71332,71331,71342,74799,74800,74803,74804,75515,75516,75520,75519,76705,76704,76703,76706,80475,80474,80476,80477,81655,81656,81657,81658,81659,81660,81661,81662,81689,81690,81691,86592,86593,86594,86595,87021,87022,87023,87098,87097,87096,87094,87095,84152,87604,84154,87603,87602,87601,84156,84153,87711,87712,87713)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}