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 (
    68905, 68906, 68915, 68914, 68913, 68912, 
    68916, 70638, 70637, 70636, 70635, 
    70634, 72105, 72104, 72393, 72394, 
    73187, 73186, 73185, 73188, 73311, 
    73310, 73496, 73497, 73498, 73499, 
    74204, 74203, 74213, 74212, 74214, 
    74938, 74939, 81485, 81486, 81487, 
    81488, 81489, 81490, 84291, 84292, 
    84293, 84766
  )

Query time 0.01677

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": 43,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68905,68906,68915,68914,68913,68912,68916,70638,70637,70636,70635,70634,72105,72104,72393,72394,73187,73186,73185,73188,73311,73310,73496,73497,73498,73499,74204,74203,74213,74212,74214,74938,74939,81485,81486,81487,81488,81489,81490,84291,84292,84293,84766)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}