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 (
    68903, 68902, 68901, 68904, 68930, 68929, 
    68928, 68927, 68926, 68925, 68924, 
    68923, 68922, 68931, 73140, 73139, 
    73138, 73219, 73218, 73217, 73216, 
    73215, 73214, 73213, 73212, 73220, 
    75729, 75736, 75730, 75731, 75732, 
    75733, 75734, 75735, 76049, 76048, 
    76047, 76050
  )

Query time 0.00541

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": 38,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68903,68902,68901,68904,68930,68929,68928,68927,68926,68925,68924,68923,68922,68931,73140,73139,73138,73219,73218,73217,73216,73215,73214,73213,73212,73220,75729,75736,75730,75731,75732,75733,75734,75735,76049,76048,76047,76050)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}