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 (
    71561, 71560, 71563, 71564, 71562, 71565, 
    71566, 71567, 71568, 71571, 71572, 
    71578, 71576, 71577, 75637, 75635, 
    75636, 76698, 76697, 78331, 78332, 
    79034, 79035, 79197, 79196, 86218, 
    86219, 86220
  )

Query time 0.00261

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": 28,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (71561,71560,71563,71564,71562,71565,71566,71567,71568,71571,71572,71578,71576,71577,75637,75635,75636,76698,76697,78331,78332,79034,79035,79197,79196,86218,86219,86220)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}