SELECT 
  pfv.feature_id, 
  pfv.product_id, 
  pfv.variant_id, 
  fv.position, 
  fvd.variant 
FROM 
  cscart_product_features_values AS pfv 
  INNER JOIN cscart_product_feature_variants AS fv ON pfv.feature_id = fv.feature_id 
  AND pfv.variant_id = fv.variant_id 
  INNER JOIN cscart_product_feature_variant_descriptions AS fvd ON pfv.variant_id = fvd.variant_id 
  AND fvd.lang_code = 'vi' 
WHERE 
  pfv.feature_id IN (
    21080, 24211, 19793, 21073, 23549, 22383, 
    20616, 24239, 23362, 23712, 19615, 
    21313, 21757, 21075, 21501, 21587, 
    20170, 21592, 21303
  ) 
  AND pfv.product_id IN (
    2435, 41286, 6070, 2442, 35217, 335, 
    3499, 41549, 32712, 36291, 6604, 1993, 
    1266, 2440, 1689, 1550, 4865, 1542, 
    2003
  ) 
  AND pfv.lang_code = 'vi'

Query time 0.03509

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "fl",
            "variant_id",
            "lang_code",
            "product_id",
            "fpl",
            "idx_product_feature_variant_id"
          ],
          "key": "PRIMARY",
          "key_length": "6",
          "used_key_parts": ["feature_id", "product_id"],
          "rows": 389,
          "filtered": 0.017086999,
          "attached_condition": "pfv.feature_id in (21080,24211,19793,21073,23549,22383,20616,24239,23362,23712,19615,21313,21757,21075,21501,21587,20170,21592,21303) and pfv.product_id in (2435,41286,6070,2442,35217,335,3499,41549,32712,36291,6604,1993,1266,2440,1689,1550,4865,1542,2003) and pfv.lang_code = 'vi'",
          "using_index": true
        }
      },
      {
        "table": {
          "table_name": "fv",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY", "feature_id"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["variant_id"],
          "ref": ["dev_db.pfv.variant_id"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "fv.feature_id = pfv.feature_id"
        }
      },
      {
        "table": {
          "table_name": "fvd",
          "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": "fvd.lang_code = 'vi'"
        }
      }
    ]
  }
}