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 = 'en' 
WHERE 
  pfv.variant_id IN (
    86406, 86407, 86467, 86468, 86469, 86470, 
    87131, 87132, 87133, 87134, 87135, 
    87136, 87138, 87137, 87144, 87149, 
    87158, 87159, 87150, 87151, 87152, 
    87153, 87154, 87155, 87156, 87157, 
    87145, 87146, 87147, 87148, 87263, 
    87331, 87330, 87332, 87334, 87333
  )

Query time 0.00607

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 (86406,86407,86467,86468,86469,86470,87131,87132,87133,87134,87135,87136,87138,87137,87144,87149,87158,87159,87150,87151,87152,87153,87154,87155,87156,87157,87145,87146,87147,87148,87263,87331,87330,87332,87334,87333)"
        }
      },
      {
        "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 = 'en'"
        }
      }
    ]
  }
}