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 (
    68327, 68328, 68330, 68329, 68331, 68347, 
    68346, 68345, 68344, 68343, 68348, 
    68352, 68351, 68350, 68349, 68353, 
    71520, 71519, 71518, 71521, 71547, 
    71549, 71551, 73305, 73304, 76827, 
    81676, 81685, 81686, 83177, 83178, 
    83179, 83180, 86606, 86607, 86608
  )

Query time 0.00582

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": 36,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68327,68328,68330,68329,68331,68347,68346,68345,68344,68343,68348,68352,68351,68350,68349,68353,71520,71519,71518,71521,71547,71549,71551,73305,73304,76827,81676,81685,81686,83177,83178,83179,83180,86606,86607,86608)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}