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 (
    68336, 68335, 68334, 68333, 68332, 68337, 
    68341, 68340, 68339, 68338, 68342, 
    76719, 76718, 78426, 79209, 79210, 
    79208, 79230, 79231, 79229, 79232, 
    79233, 79234, 79244, 79242, 79243, 
    81505, 81506, 81507, 81508, 81665, 
    81666, 81672, 81673, 74389, 82449, 
    82450, 74391, 74392, 74393, 74394, 
    74395, 74396, 74397, 74399, 74407, 
    82455, 74412, 82456, 84396, 84397, 
    84398, 84399, 84400, 84426, 84427, 
    84428, 84429
  )

Query time 0.02435

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": 58,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68336,68335,68334,68333,68332,68337,68341,68340,68339,68338,68342,76719,76718,78426,79209,79210,79208,79230,79231,79229,79232,79233,79234,79244,79242,79243,81505,81506,81507,81508,81665,81666,81672,81673,74389,82449,82450,74391,74392,74393,74394,74395,74396,74397,74399,74407,82455,74412,82456,84396,84397,84398,84399,84400,84426,84427,84428,84429)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}