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 (
    70581, 70580, 70582, 70722, 70721, 70720, 
    70719, 70718, 70723, 70728, 70727, 
    70726, 70725, 70724, 70729, 76917, 
    76915, 76916, 79647, 80915, 80916, 
    82389, 82393, 82392, 82391, 82390, 
    82662, 82663, 82664, 82665, 82666, 
    82667, 82668, 84766, 84292, 84293
  )

Query time 0.00567

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 (70581,70580,70582,70722,70721,70720,70719,70718,70723,70728,70727,70726,70725,70724,70729,76917,76915,76916,79647,80915,80916,82389,82393,82392,82391,82390,82662,82663,82664,82665,82666,82667,82668,84766,84292,84293)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}