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 (
    68396, 68397, 68399, 68398, 68400, 73187, 
    73186, 73185, 73188, 73311, 73310, 
    74204, 74203, 74213, 74212, 74214, 
    74938, 74939, 78274, 78273, 78272, 
    78271, 78270, 78275, 78429, 78428, 
    78430, 79220, 79222, 79221, 79638, 
    79639, 79652, 79653, 84147, 84148, 
    84149, 84766, 84292, 84293, 85226
  )

Query time 0.00596

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": 41,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68396,68397,68399,68398,68400,73187,73186,73185,73188,73311,73310,74204,74203,74213,74212,74214,74938,74939,78274,78273,78272,78271,78270,78275,78429,78428,78430,79220,79222,79221,79638,79639,79652,79653,84147,84148,84149,84766,84292,84293,85226)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}